Cutting the Presumpscot rail bridge would not cut Portland off from the rest of the US, nor cut the route between Portland and Richmond, Quebec.
My apologies, it would have taken cutting both bridges over the Presumpscot, or alternatively landing and taking Yarmouth Junction.
Or landing with a brigade and cutting the Saco bridge.
Both of these options would render the Grand Trunk route non-viable, though only the latter would cut off Portland.
The Canadian winter is lethal for the unprepared, but troops could be moved during that time. In actual history, the British moved five infantry battalions and nine artillery batteries from St John, New Brunswick to Quebec City between January and March of 1862. Period British expert Colonel McDougall believed that Union advantages in men, material, and supply would
overcome the difficulties of a winter campaign and consensus among British leadership appears to have been that the Union would have breached the St Lawrence
before spring.
Ah, I see the source of confusion - that discussion (that the Union would breach the St Lawrence before spring) was based on the assumption that the Union had already done all the planning necessary to straight-away transfer forces from the south to overrun Canada before reinforcements arrived; that is, that the Trent incident was the final step in a deliberate campaign of provocation intended to allow the Union to drop a war (with the South) it was losing by the excuse of a new war with Britain.
As for the difference between moving five infantry battalions by a pre-established sleigh route in friendly territory over the course of three months (at a peak rate of about two companies a day) and launching a major invasion force into enemy territory, this should be so obviously different it doesn't bear bothering to explain. (The exact wording was 'a large force can only move and keep the field for about five months in the year. viz.,from about the middle of May to the middle of October... between the middle of December and the end of March, the intense cold forbids an army encamping, and the deep snows prevent the movement of troops... from the beginning of April to about the middle of May the state of the roads owing to the thaw of the winter snows, is such that many are impassable for an army.')
It is probable that the British would destroy Victoria Bridge in Montreal and the Grand Trunk crossing at the Richelieu River, but that also means the British won't be able to use those routes for an offensive. It also doesn't stop what Colonel McDougall thought was the best plan for the Union,
using canals and Lake Champlain to get to Rouses Point.
And that won't work until spring, self-evidently, because Lake Champlain freezes over in winter. It doesn't thaw out until the start of May, after the St Lawrence has been ice-free for a month.
As for Victoria Bridge, the British can use shipping to cross the river, and similarly they can use their control of the St Lawrence to move troops and supplies between Montreal and Quebec - or just use the Richelieu River as a supply route directly, covered by Clown class gunboats.
Why would either the Montreal or Quebec forces advance on Richmond instead of staying behind their defensive works? Especially since the Union could destroy the tracks between Richmond and whichever of Montreal and Quebec the Union doesn't decide to attack.
Because the British are not NPCs and are able to act to inconvenience the Union.
Incidentally, you may not have fully thought through that suggestion about destroying the tracks - if it's easy to destroy large stretches of rail track then the British can do it before the Union arrives (and put the kibosh on the offensive) but if it's not easy then the British can just march however far it is to Richmond that their new rail head is.
How far up the "wrong route" are you imagining the Union marching and destroying the rail line?
Whatever happened to your
claiming that the Union had
no plan for using more than a few regiments.on the Canadian border?
It's still sustained - it's the difference between plans to move actual troops (which were basically non-existent for more than the odd regiment, and show me if I'm wrong) and a feel of the superior grand strategic approach.
I'd also be interested in what your source is for "the Union's most respected military minds were in agreement that the Rouses Point route had the most chance of success'? The only person I've found who seems to have held that view was the British expert, Colonel McDougall, who felt the Union's best route was using canals and lakes to get to
Rouses Point, not railroads.
Via Cerebro:
There are a lot of possibilities, but the Montreal attack is very likely. For a start, Montreal was targeted in both 1812 and 1813 (and 1775, of course). Secondly, in the war of 1812, any success the US enjoyed in Ontario did nothing to shake the British hold on Canada. Thirdly, given the increased power that breech-loading artillery, entrenchments, and the rifled musket gave to the defensive, I can't see the Union army wanting to batter its way up the Niagara peninsula at the cost of tens of thousands of casualties. In fact, if we'd suggested such a pointless and bloody thrust instead of a quick, aggressive and strategic movement against the heart of British power in Canada, we'd probably have been accused of making Union generals into idiots who are doing the exact same thing that failed them previously, but losing more heavily as a result.
Fourthly, we do have the pre-war thinking of the Union army to show which way they were going. Fifthly, this pre-war thinking seems to have been confirmed in part by Totten's instruction to concentrate at Albany- which suggests it wasn't completely outdated. And, sixthly and lastly, the 1862 report by the British commissioners further confirmed this thinking:
'15. The probable plan of the enemy would be to place corps on all these assailable points, to oblige a dispersion of the troops along the whole frontier, turning these feints into positive attacks, if circumstances rendered it advisable.
The main attack would undoubtedly be directed from the head of Lake Champlain on Montreal... the capture of the important city of Montreal would sever the communications between Quebec and the upper province, and would paralyze the defence of the country.'
As, indeed, did Jervois's 1864 report:
'[4.] the Americans could collect a large force within 40 miles of Montreal, and between that place and Rouse's Point the country is so flat and open that to the westward of the Richelieu river... there is no obstacle to the advance of an enemy, in the summer season, over any part of it.
5. Montreal being moreover at the head of the sea navigation of the St Lawrence, and the focus of all communications by land and water between the Eastern and Western Districts, as well as between Upper Canada and the Maritimes provinces... [is the] strategical capital of the country. If Montreal were taken, the whole of Western Canada would be cut off from support either from Lower Canada or from the Maritime Provinces.'
Henry Halleck's 1846 '
Elements of military art and science' goes through the US army's pre-war planning for an invasion of Canada.
'A base may be parallel, oblique, or perpendicular to our line of operations, or to the enemy's line of defence. Some prefer one plan and some another; the best authorities, however, think the oblique or perpendicular more advantageous than the parallel... An American army moving by Lake Champlain, would be based perpendicular on the great line of communication between Boston and Buffalo; if moving from the New England states on Quebec and Montreal, the line of operations would be oblique ; and if moving from the Niagara frontier by Lake Ontario and the St. Lawrence, the line would be nearly parallel both to our base and to the enemy's line of defence — an operation, under the circumstances, exceedingly objectionable.'
'We are fully aware of the great advantages to be derived from the reduction of Quebec; and we are also aware of the great difficulties to be encountered in any attempt to accomplish that object. It may, and probably will ere long, be made to surrender to our arms ; but it would be utter folly to base our military operations on the contingency of a short and successful siege. By advancing upon Montreal by the Lake Champlain route, we could cut off the Canadian forces in the West from all reinforcements; and then, as circumstances might direct, could besiege Quebec, or attack the enemy in the field, or perhaps, manoeuvring as the French did at the siege of Mantua, accomplish both objects at the same time.
'We have seen that it was one of Napoleon's maxims that an army should choose the shortest and most direct line of operations, which should either pierce the enemy's line of defence, or cut off his communications with his base. It is the opinion of men of the best military talent in our army that the Lake Champlain line satisfies all these conditions at the same time... All agree that the St. Lawrence above Quebec constitutes the key point of the enemy's defence, and the objective point towards which all our operations should be directed. To reach this point, all our Boards of Engineers have deemed it best to collect our troops at Albany and advance by Lake Champlain, a distance of only two hundred miles. Besides the advantages of a good water communication the whole distance for the transportation of military stores, there are several roads on each side, all concentrating on this line within our own territory. It has already been shown by the brief sketch of our northern wars, that this line has been the field of strife and blood for fifteen campaigns. Nature has marked it out as our shortest and easiest line of intercourse with Canada, both in peace and war. Military diversions will always be made on the eastern and western extremities of this frontier, and important secondary or auxiliary operations be carried on by the eastern and western routes ; but until we overthrow the whole system of military science as established by the Romans, revived by Frederick, and practised and improved by Napoleon, the central and interior line, under all ordinary circumstances, will furnish the greatest probabilities of success.'
'It is agreed upon all sides that the British must first collect their forces at Quebec, and then pass along the line of the St. Lawrence and Lake Ontario to reach the Niagara and Detroit frontiers. Our boards of engineers have deemed it best to collect troops on the Champlain line, and, by penetrating between Montreal and Quebec, separate the enemy's forces and cut off all the remainder of Canada from supplies and reinforcements from England.'
Russel H. Beatie's second volume on the Army of the Potomac, dealing with the period when McClellan was down with typhoid:
'The president had relied on Scott. He was gone. Now, he relied on McClellan; but he was incapacitated. He turned to the Library of Congress- it would always respond- for standard texts on strategy and military affairs, including Halleck's Elements of Military Art and Science.' (page 433; note 13 cites Miers, Lincoln Day by Day, January 8 1862)
'To defend the northern frontier... We should have adequate means of transportation at command to be able to speedily concentrate on the St Lawrence a force of acknowledged competency to take possession of the canal and of Montreal, and hold them. The possession by the United States of the outlets of Lake Ontario, and of Montreal and its communications, would cut off all supplies from the Canadians, and leave them to an unsupported and hopeless conflict with all our forces.' (House of Representatives Report No. 8
6, Permanent Fortifications and Sea-Coast Defences,
23 April 1862)
This should make pretty clear that there was a general focus on attacking against Montreal.
More correctly, De Joinville was commenting based on his experience with
George McClellan, who probably was incapable of more than one days march away from his base of operations. In actual history, Grant, Sherman, Lee, Jackson, Early, proved De Joinville was wrong, as had Scott in the Mexican-American War.
McClellan is not a caricature of universal incompetence. He's the first person in the Union to develop the flying column method of supply into proper use, and is generally considered a skilled organizer even by those who are his detractors.
Lee, Jackson and Early are Confederate generals not Union.
Grant and Sherman surely did, yes - but in early 1862?
And Scott couldn't have shown it possible to operate a large 1860s-type army away from supply because he didn't have one - his force was smaller and largely composed of regular troops (which manage that sort of thing more easily).
Do you expect the Army of the Potomac to become more competent with supply because the troops in it have moved north?
Union rails in New England mainly used the "Portland Gauge", which was the same as the "Provincial Gauge" used by the the Grand Trunk Railroad.
And I'm talking here about the rail lines in Upper Canada / Canada West / Ontario. You'll note I'm focusing on cutting the Grand Trunk as the viable way to impede progress there, but for Union troops crossing from Detroit into Canada 5'6" locomotives would have to be built on site if they can't capture any - the rail line from New England to Detroit is 4'8.5" and won't fit them.
As noted above, consensus among British leadership appears to have been that the Union would have breached the St Lawrence
before spring. The First Lord of the Admiralty did not think the Great Lakes would be British lakes, he thought "
perhaps with proper arrangements we might defend Lake Ontario and Kingston Dockyard".
Yes, the British are pessimistic sometimes (note that, again, this is in the context of the Union launching an attack in late November or early December - an attack for which we have incontrovertible evidence they were not preparing, because they didn't have a corps in place before the climbdown). But how exactly
would the Union breach the St Lawrence before the spring thaw? The method you've been suggesting is moving by lake and canal to Rouses Point (not possible before the end of April) by which point the spring thaw's been going on for a month, the advance is against troops with three months of drill in entrenchments, and there's a corps of regular British infantry to defend Montreal specifically; or going up the Grand Trunk (which functionally means moving a brigade at a time up the rail line, because the bit about it being impossible for a large army to encamp in winter means you can't march
along the rail line and have to travel
by the rail line).
Of course, the latter is also vulnerable to the British dropping another bridge - the bridge at Norton/Stanhope, just north of the Canadian border - in addition to all the other methods we've discussed.
Have you got a better source for these plans than
67th Tigers? Or any indication of how soon the Btirish thought they could have these fortifications completed, manned, and armed?
The British thought it'd take some time to do them all as permanent works. On the other hand, doing them as temporary earthworks would be quite possible in extremis - they
do have several months of prep time and a lot of idle labour in the Province.
It's true they didn't have the plans in place ahead of time, but even some quite rustic versions would increase the difficulty greatly.
As for the source, yes, I've seen the original report by the commissioners for the defence of Canada. 67th's transcript is fundamentally correct.
And as for arming and manning them - manning them involves calling out two flank companies of militia per registered militia battalion, and the first flank company was called out before the end of the crisis with the second awaiting arms shipments (up the sleigh route). This mobilization was cancelled OTL, but I estimate that in the event of a continuing crisis escalating to war they could have called out the second flank company by mid-January.
And arming them is entirely doable, there's enough guns already in Canada in storage and the only thing needed is to build enough gun carriages (which would take time, sure, but there's months) and move them into place (they have rail lines to do much of it).
Contrast this (they've got the guns, they've got the men, they've got the money too) with the state of defence of the US East Coast (where Totten was quite clear he did not have enough guns in storage to properly defend just Massachusetts). I don't have any trouble with the assumption the US would find hundreds of coastal artillery pieces in a sock drawer or something, my complaint about defending the US East Coast is solely predicated on the need for large numbers of troops to prevent a British landing given other Union requirements.
The British have no other requirements for their Canadian militia than defending Canada.