Civil War Sealion: The Capture of Washington, D.C.

Here on the boards, the term "Sealion" has become a watchword for a commonly-known, but extremely unlikely alternate history. Virtually everyone here knows about Hitler's plans for the invasion of England, and almost as many people know about the problems associated with any invasion -- the lack of effective transport, insufficient training for the landing force, the continuing resistance of the RAF, and the undimmed might of the Royal Navy. All these factors combined to foil the invasion. On the surface, a successful invasion seems likely, but as we examine the facts, the truth comes out -- it simply wasn't possible.

The American Civil War is no more immune to these Sealion moments than is the Second World War. One instance in particular stands out, however -- capture of Washington, D.C. by the Confederacy. Despite innumerable stories and threads discussing the contrary, at no time during the course of the war was the Army of Northern Virginia in position to capture the Union capital. Insufficient forces, a shaky logistical train, Union defenses, and the personalities of those involved make it virtually impossible for the Confederacy to have captured Washington during the war.

In 1863, Washington could boast over 60 forts and 93 batteries containing 837 guns and manned by 25,000 men. The defenses of Washington contained more artillery than the combined total of the Armies of the Potomac and Northern Virginia. 13 miles of trenches supported the forts, which were arranged in a then-unique supporting structure. Rather than standing alone, the forts of Washington contributed to each others' defense, and were positioned so they could cover the dead spots in their neighbors' fields of fire. This was a new development in the history of fortifications, and the technique would be used in both of the World Wars and every war since. At the time, Washington was the best-defended city in the world. Until the trenches of the First World War were dug, no fortification system in the world even came close to the interlocking system of defense that covered Washington.

A contemporary army would be forced to besiege, batter, and wear their way through the defenses in a costly, months-long (if not years) campaign. During that time, the attacking army would be vulnerable to the Union Army outside the defenses, while the city's defenders would continue to receive supplies via seaborne supply lines protected by the US Navy. The entire perimeter of the defenses was 37 miles, necessitating a massive covering effort required to besiege the city would leave the attackers vulnerable to an outside army coming to relieve the city. The sheer logistics of a siege make it impossible to attempt.

Of course, if you have a Point of Departure prior to the beginning of the war or even the intervention of Alien Space Bats, all these arguments go out the window. The best instance of this is in Harry Turtledove's Guns of the South, in which Confederate forces armed with AK-47s are able to overrun the Washington defenses to capture the city. Even this scenario, however, has its problems -- Turtledove conveniently overlooks the existence of two additional bridges across the Potomac (Long Bridge is listed as destroyed in the text) that would have allowed Grant's forces to reinforce the city and prevent its capture. Even with weaponry nearly a century more advanced, the capture of Washington in GoTS is a close-run event.

In our timeline, of course, the Confederate Army of Northern Virginia did not have AK-47s. Indeed, until the capture of the Federal arsenal at Harper's Ferry in 1862, there weren't enough rifled muskets to arm the entire Confederate force with the most modern weapons. The shortage of weapons wasn't limited to individual weapons -- the Confederacy had a severe lack of artillery as well. In 1861, more guns were produced in the state of New York alone than in the entire Confederacy. This lack of heavy artillery would hamper Confederate armies at every turn, and if the Army of Northern Virginia had attempted to capture Washington, this lack would have been a massive disadvantage. If, of course, the guns could even get into range.

That fact is not one to be disregarded. During the entire course of the war, Washington came under direct, large-scale attack only once. In 1864, 20,000 Confederate soldiers under the command of Gen. Jubal Early snuck across the Potomac and attacked the northwestern defenses of the city in an effort to distract U.S. Grant from his attack against Richmond. After trying to force the defenses for two days, Early's force retreated. Confederate forces never even reached the walls of Fort Stevens, the main fort under attack.

Though this was one isolated event, the Army of Northern Virginia did have three main opportunities to attack Washington: in the wake of the Battle of Bull Run, during Lee's Maryland invasion, and during what would become known as the Gettysburg Campaign.

(To be continued...)

Nice write-up, looking forward to more.

I thought this was going to be the story of how Washington DC fell to a Confederate amphibious attack.

But don't let me discourage it! it looks good.

Even before the Battle of Bull Run, work had begun on the defenses of Washington, D.C. Initial barricades had been prepared within the city, and in May, work began on forts to protect the Virginia ends of the Aqueduct Bridge and Long Bridge. These works were expanded in the seven weeks between the occupation of Arlington and Alexandria and the Battle of Bull Run. More than half a dozen forts and batteries sprang up along the banks of the Potomac. They were small, independent works intended to defend the bridges across the river, but they were a start.

The work was interrupted by the Battle of Bull run. Engineers working on the fortifications were swept south with the Army of Northeast Virginia. In the wake of the disastrous battle, Washington was swept with the fear that the Confederate Army was about to sweep down upon the city.

We now know that the Confederate forces involved in the fighting were in no condition to conduct a pursuit. The initial stages of the battle had badly shaken the Confederate regiments, and only the intervention of Gen. Jackson's Virginians prevented a Confederate defeat. From a force of 33,000 at the beginning of the battle, the Confederates could muster fewer than 30,000 troops in still-green regiments.

But what if they had engaged in a pursuit? The short answer is that they couldn't. This was the first battle the soldiers had fought in, and many were suffering from what would later become known as post-traumatic stress disorder. In addition, the companies and regiments involved in the fighting had become disorganized. Any immediate pursuit would have resulted in a Confederate force no more coherent than the Union men they were chasing. Any exhausted Confederates arriving at Washington in fighting order would then face the Potomac forts and a handful of fresh (though green) regiments bivouacked in and near the city, in addition to whatever veterans of the battle had managed to reform.

But what if the Confederates had regrouped, first? They'd be facing a new Union commander -- General George McClellan, who assumed command six days after the battle -- and a new series of earthworks, which McClellan had ordered in the first days after assuming command. The Union forces would've had time to regroup as well, and would have been bolstered by fresh regiments brought in by train from the north. The new Army of the Potomac that replaced the Army of Northeast Virginia was stronger and more experienced than its predecessor.

But the odds would be far better than those later in the war. An advance on Washington in August or September would have been the Confederates' best chance to capture Washington. This period in time was similar to what would be experienced by Great Britain in the summer of 1940. By Christmas 1861, the forts begun by General McClellan were finished, so any successful attack on the city would have had to have taken place before that date. The Confederates would have had the momentum, better (though not good -- the Union would still have several thousand more troops available) odds, and would avoid the need to break through the massive defenses built later.

But they would be facing General George McClellan. Today, McClellan is derided as a sluggard -- someone who couldn't move quickly, who didn't take advantage of his numerical superiority, and who was never fully happy with his logistics. In a fight for Washington, all of his disadvantages would have been nullified. He would be facing an enemy that was coming directly to him -- there would be no need to hunt for the Confederate force. He would be fighting from a prepared defensive position, not out in the open field. And he would be fighting with the entire might of the Army of the Potomac and the garrison of Washington, D.C.

The situation might be likened to that of General Bernard Law Montgomery in the Battle of El Alemein. Like McClellan, Montgomery was cautious, liked to stockpile men and equipment before an offensive -- often to excess, according to each man's detractors. Like El Alemein, the Battle for Washington would be a set-piece battle, working to McClellan's strong suit. There would be no need to maneuver, no need to execute complex orders in order to bring all of his men into battle. As commander of a battle for Washington, McClellan would do as well, if not better than, any general in the Union Army, including Ulysses S. Grant.

An attack against Washington in the fall of 1861 would still be a ferocious fight. But it would be a Union victory. Fighting from prepared positions, with greater numbers of soldiers and artillery, and with a firm supply line, it would be a massive victory for the North.

In the end, the Confederate leaders could see exactly what I've just laid out here. They did not attack Washington for those very reasons -- to do so would to play into the hands of the North. And after all, their war was a primarily defensive one. The South could win simply by continuing to exist. It was the North that had to go on the attack, which it did with the Peninsula Campaign. That campaign would in turn spark the next chance for the Confederacy to attack Washington -- The 1862 Maryland Campaign.

In the fall of 1862, the Army of Northern Virginia, commanded by Gen. Robert E. Lee, crossed the Potomac and invaded Maryland. The invasion had many purposes, the most important of which was to attempt to recreate the 1777 Battle of Saratoga, which had brought France into alliance with the nacent United States. Jefferson Davis and Gen. Lee both hoped that a major victory on Union soil would bring France and Great Britain into the war on the side of the Confederacy. In OTL, that wasn't to be, thanks to the interception of Lee's General Order 191, which allowed McClellan to force Lee into battle at Antietam. The result was the bloodiest single day of fighting in the entire American Civil War and forced Lee's forces south, back across the Potomac.

So what happens if Lee's Lost Order isn't lost? Harry Turtledove's Southern Victory Series (Timeline 191) provides one possible answer. According to the introduction of How Few Remain, Lee would have continued north and east, eventually meeting the Federal army in combat somewhere in Pennsylvania. Thanks to the inept generalship of McClellan, the Union army would have been defeated and the Confederates could have continued onward to Philadelphia, or so goes the story.

In that story, Lee chooses not to attack Washington, but instead goes for the comparatively undefended Philadelphia, discouraged from attacking Washington thanks to that city's defenses. But let's use Timeline 191 as a starting point for our scenario, but instead of moving east after the meeting engagement in Pennsylvania, let's have Lee move south. After all, reaching Philadelphia would extend Lee's supply lines possibly beyond the breaking point and leave him vulnerable to encirclement.

Moving south after the hypothetical Pennsylvania battle, Lee would have faced a hostile countryside and scattered Union units determined to bring him to battle and slow his army's progress. 1861 Baltimore riots notwithstanding, the vast majority of Marylanders were staunch Unionists, and in OTL's campaign, Lee had to forcibly requisition much of his army's supplies. This would be the case in this scenario as well. The end result is that his progress will be slowed, allowing for the Union Army of the Potomac to regroup and resume the pursuit.

If Lee chooses to attack Washington in this scenario, he will do so against a defensive presence that is fully aware and ready to meet him. In OTL's Battle of Antietam, Lee could muster 45,000 troops. If we imagine 10,000 casualties at the hypothetical Pennsylvania battle, that would leave approximately 35,000 able-bodied fighters to face Washington, a city with 25,000 dedicated defenders. Add in the 5,000 Union army soldiers present in the city but not assigned to it, and Lee will be facing approximately 30,000 entrenched, forewarned soldiers defending their capital city.

This will not be a surprise attack as was 1864's Battle of Fort Stevens. The defenders will be alert, waiting, and have numbers nearly equal to those of Lee's forces. In addition, the Union Army will still have nearly double Lee's strength (imagining 20,000 casualties from the Pennsylvania battle) with over 70,000 men. They will be somewhat demoralized, and will no doubt have a new commander following McClellan's defeat, but after they regroup, they will be a force to be reckoned with, particularly if Lee is involved in a lengthy struggle to capture Washington.

To conclude: In order to capture Washington in the 1862 Maryland Campaign, Lee would have had to meet and defeat the Union army in the field, advance south, break through the massive defenses protecting Washington, defeat the ~30,000 defenders of Washington, all before the rapidly-approaching winter. Lee would have to defeat over 120,000 men in two battles, with fewer than 45,000 of his own men. They'd have to attack Washington with the threat of the reconstituted Union Army approaching from the rear. And they'd have to do it quickly, before the September autumn turns into the snows of winter.

It's no less impossible than the task facing the German Army in the summer of 1940.

If he cannot take Washington, Lee will be forced back across the Potomac, much as he did in OTL after the Battle of Antietam. The victory at Washington would then allow Lincoln to issue the Emancipation Proclamation, which would put an end to any thoughts of European involvement, particularly in light of Lee's failure to capture a major city like Washington or Philadelphia.

Lee's final chance to take Washington would be in the wake of a victory at the Battle of Gettysburg. If Lee could somehow win at Gettysburg without taking overwhelming casualties (no small feat in itself), the door might be open for an advance on Washington -- but even that would be an impossible task.

William Forschen does an excellent job with this particular scenario in his Gettysburg three-book series. In the first book of the series, he details a Confederate victory at the Battle of Gettysburg, followed by a Confederate advance on Washington. Lee attacks Fort Stevens in an attempt to capture Washington, and is bloodily repulsed. It's a fantastic sequence of events, and very well-written. What problems I have with the series don't show up until later books.

Many of the problems that face Lee in the 1862 scenario are still present in this one as well. Any prolonged attempt to take Washington brings the threat that the Army of the Potomac will regroup and take Lee in the rear. The defenses of Washington are simply too strong to take in a single quick stroke, and with the threat of the Army of the Potomac, Lee cannot afford to be pinned down in a protracted campaign for the city. If he hurts the Army of the Potomac badly enough, a city like Baltimore might be open to his troops, but not Washington -- it's simply too well defended.

Throughout the war, the defenses of Washington never stopped growing. New blockhouses were built monthly, and forts popped up wherever there was a dead spot in the terrain. In April 1865, even when it was clear that the Confederacy couldn't threaten the city, two new blockhouses were constructed, and at the time of Lee's surrender, four more were being built. Forts were under constant remodeling and expansion from the time they were constructed to the time of the armistice. New magazines and bombproofs were constructed seasonally, and training was perpetual.

At any time, the capture of Washington would have faced three insurmountable problems -- first, the massive number of forts, guns, batteries, blockhouses, trenches, bunkers, bombproofs, magazines, and depots within Washington. These could not be taken by infantry assault alone. An attacking army would need siege artillery of its own in order to break the defending forts, then be willing and able to suffer the casualties involved in an attack against the forts' defenders.

Second, the threat of the Army of the Potomac was an ever-ready knife to be stabbed in the back of any attacker. Even if an attacking army defeated the Army of the Potomac, the time needed to break the defenses of Washington would allow that elastic force to rebound from defeat, just as it did after half a dozen other defeats at the hands of generals like Lee and Longstreet. Then, an attacking army would be stuck between the rock of Washington and the hard place of the Army of the Potomac.

Third are the logistical and manpower problems facing any attacker. Even if the Army of the Potomac is defeated, it will inflict heavy casualties on the opposition. The South does not have an unlimited supply of soldiers or equipment, and if the battle is costly enough, an attack on Washington may very well be impossible given the numbers involved. At the battle of Gettysburg, the Army of Northern Virginia could muster just under 72,000 troops. It suffered roughly 23,000 casualties in that fight, as did the Union Army, which was in a defensive position. Attempting to take Washington so soon after even an alternate Gettysburg could well mean the complete collapse of the Army of Northern Virginia. Unlike the Union Army, which could draw upon the enormous population of the North, the South could not afford the loss of the ANV, and that's exactly what would happen if the Confederacy attempted to take Washington.

Wouldn't they have been better served going for Baltimore or even Philadelphia?

Calgacus said:

Wouldn't they have been better served going for Baltimore or even Philadelphia?

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That's not what I'm saying here. I'm simply saying that the capture of Washington is to the Civil War what Sealion was to the Second World War. It's impossible, given the circumstances on the ground at that time. It's ASB.

In Mackinley Kantor's If the South Had Won the Civil War, I think, the South controls regions surrounding Washington D.C. They don't actually capture the city, but the city would end up being an enclave, surrounded by a hostile Confederacy, and the North doesn't want that. It's a painful decision, but the North is forced to give up D.C. and the capital is moved to Columbus, Ohio.

The other question is this, would capturing DC have won the Civil war for those who wished to keep humans as property. I suspect that it is more likely to have energised and mobilized the people of the North to the lawful elected government of the United States.

Storming DC is close to ASBish, but WI the Confederates just had surrounded the city, trying to starve it?

Washington's defences

I'm sure Vauban would beg to differ about forts with interlocking fields of fire. It is a technique he perfected during the 17thC.

Max Sinister said:

Storming DC is close to ASBish, but WI the Confederates just had surrounded the city, trying to starve it?

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I had considered that, but they don't have the troops to do so indefinitely. The time needed for a siege would allow the Army of the Potomac to reform as it did countless other times, and descend upon the besiegers, who will be scattered across the enormous perimeter of the District. In addition, it'd be very difficult for them to close off the Potomac River to Federal shipping. I'm not saying that it couldn't be done, simply that it would add to an already impossible cost for the Confederacy, making it far easier for their destruction when the Federal army arrives.

Larrikin said:

I'm sure Vauban would beg to differ about forts with interlocking fields of fire. It is a technique he perfected during the 17thC.

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I stand corrected.

This is, of course, if the Confederacy stands alone, and Britain and France do not decide to intervene on their behalf . . .

Actually, the only time the CSA could have had a chance of successfully taking Washington, at least according to certain claims, was following First Bull Run. The Union troops were highly disorganized, but so were the Confederates. If the Confederates organized fast enough, this could lead to...

Union worst case scenario: The Confederates catch the Union by surprise in the hysteria following the Battle of Bull Run. The Union forces are mostly disorganized and don't deploy fast enough to exploit the defenses around the city. The Confederates gain enough ground by the time the Union troops do get around to getting their forces in place, but much of the government has fled Washington by this time and morale among the troops is extremely low. The city falls to the Confederates, but at a heavy price. The capture of the city does improve the Confederate image abroad, but Britain and France still won't back the Confederacy. With the capital under Confederate control, the US holds its temporary capital in Philadelphia. My analysis: Not very likely.

Confederate worse case scenario: The Confederates are spotted by Union scouts. The troops rally to man the defenses of the city. The Confederates find their enemy ready for them and they want revenge for the Battle of Bull Run. The Confederates are soundly repulsed by the Union defenses after suffering enormous casualties and they retreat into Virginia. Rallied by this morale boost, the Union marches south without much opposition to capture Richmond. The war is over. My analysis: Very likely.

No-win scenario (mixture of both): Confederate troops are eventually met Union troops in the city and begin to face heavy casualties. The defenses of Washington provide some response to the oncoming Confederates, but both sides are hurting. Unable to stomach the bloodbath, Johnston and Beauregard begin the retreat. Both sides are badly hurt and it is only a phyrric victory for the Union. They've protected their capital, but at a heavy price and are thus unable to pursue the Confederates back into Virginia. The South lives to fight another day. My analysis: What?

Limited action - Successful Confederate Raid: The Confederates organize a raid (similar to Jubal Early's raid in 1864), only this sends the message that the Confederates can attack the Union where it hurts. Though riskier than a real attempt to capture the city, the success of the raid into the area surrounding Washington and a brief skirmish outside the capital drives the message home and the morale of Union troops drops even further. My analysis: Likely.

Limited action - Failed Confederate Raid: The Confederates opt to raid the area surrounding Washington, but are unable to achieve most of their objectives. A brief skirmish sends the Confederate troops retreating in Virginia before they even reached the outskirts of Washington. This ultimately has no impact on the war at large save reinforcing the idea that invading the north is a bad idea. My analysis: Likely.

Defensive action: No explanation needed.

Larrikin said:

I'm sure Vauban would beg to differ about forts with interlocking fields of fire. It is a technique he perfected during the 17thC.

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I was also about to mention Vauban.


Has there ever been a thread about inverse Sealion like moments?

By that I mean things in OTL that if turned out differently would make people assume they would have been inevitable.

The Russo-Japanese War might be one of those.

Had there not been a revolution in European Russia, the manpower superiority of Russia would have eventually steamrollered Japan out of Asia through Korea.
In that time, the two maxims of 'don't attack Russia when they have space to trade for time' and 'don't fight a land war in Asia' could have been combined.
People would look back and shake there heads at the Japanese idea they could succeed where Napoleon failed.

Ace Venom said:

Actually, the only time the CSA could have had a chance of successfully taking Washington, at least according to certain claims, was following First Bull Run. The Union troops were highly disorganized, but so were the Confederates. If the Confederates organized fast enough, this could lead to...

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Agreed. Their best chance was in the first two months following the battle. The problem with that idea is that the Confederate forces were very nearly as shocked by the battle as the Union forces. No one expected the battle to be as bloody as it was -- contemporary newspaper and journal accounts report that each side expected the other to run as soon as the first shots were fired.

The Union forces were badly strung out by their retreat, but I'd argue that a hurried advance in the wake of the battle would've strung out the Confederates nearly as much as the Union forces. Then, arriving at Washington, they'd face fresh Union regiments from the north, the half-dozen forts built before the battle, and whatever troops could be scraped up from the retreat. Strung out from the advance, they'd be annihilated. Whatever survivors make it to the river will be stopped by the gunboat flotilla that sailed up and down the Potomac during the first year of the war, protecting Washington.

It's basically July 1940 all over again. If the Confederates could get there, they'd capture the city. But, like the Germans eighty years later, getting there intact was the hard part.

Excellent analysis Amerigo. Really impressive. You should consider putting this into the Timelines/Scenarios subforum

DMA said:

Excellent analysis Amerigo. Really impressive. You should consider putting this into the Timelines/Scenarios subforum

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I will, but I wanted to get some feedback first in order to address any problems people might have found with the idea.

DMA said:

Excellent analysis Amerigo. Really impressive. You should consider putting this into the Timelines/Scenarios subforum

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What DMA said.

I am struck by many of the similarities between the Confederates taking Washington DC and Sealion. Of those the fear the North/Britain had vs. the (in hindsight) lack of real intent by the South/Germany seems to be the most interesting.

Before jumping into the Final Countdown again, I'll be editing this and posting it in the TL's section of the forum. If anyone has any more comments, speak now or forever hold your peace.