2 years later and I finally post in this subsection!
So, my question is how would WWII be altered if Spain and Turkey join in?
It matters a great deal how, when, and on which side.
Spain presumably joins the Axis around 1942 during Operation Torch
Extremely unlikely if Franco is in charge. He put an impossible price on Spain's joining the Axis in 1940, at the zenith of German power. By 1942, Germany was in a lot of trouble and the U.S. was in the war. It would be suicide for Spain to enter the war then.
1940 is barely possible. Franco said he was willing, for the right price. But the price he set (in terms of fuel, food, and military aid) was more than Hitler would (or perhaps could) pay. Opinion is divided between those who think Franco deliberately highballed the price to insure that Hitler could not meet it, and those that think Franco simply overestimated Spain's value to the Axis.
But let's say that Hitler decides to be tricky. He agrees to give Franco what he demands, and gets his agreement to enter the war in writing and before witnesses. Germany can't actually deliver all the stuff, but he'll work that out later, after the victory. The important thing is to get Francho in too deep to back out.
What about Turkey?
First, continue the 1940 narrative. Hitler returns from the meeting with Franco (which was 23 October), and summons Mussolini to a meeting, where he informs him of Spain's coming entry. Hitler says Italy's resources (especially the Navy) will be needed to support Spain and attack Britain in the Atlantic.
Mussolini decides to scrap his invasion of Greece.
On November 20, Spain declares war. Britain's reaction is prepared, as ULTRA gave substantial warning. Gibraltar cannot be saved; that is, while the garrison can hold out in the Rock, the naval base, airbase, and gun batteries are all wiped out within two weeks. However, a British task force seizes the Canary Islands before German airpower can base there.
The Canaries become the anchor of British naval and air power in the region, and help limit Axis attacks into the Atlantic. These attacks are more dangerous than OTL, because they start further west, from bases the British cannot blockade - around Cadiz and south of Cape Finistere.
The German battlecruisers
Scharnhorst and
Gneisenau reach Spain after a raiding cruise. They are joined by some of the fast Italian battleships; there is now a serious threat to any British convoy without at least two battleships for protection. The threat is neutralized for a while by a carrier raid on Cadiz in January 1941, but the loss of
Furious and
Hermes to U-boats (while escorting convoys) cripples the Royal Navy.
Meanwhile, however, the British army in Egypt attacks Italian forces in Egypt and eastern Libya, winning a complete victory. Hitler responds to the British success by sending some German motorized forces to assist the Italians, under the command of Hermann Hoth, who had been a successful corps commander in France.
** NOTE: This is a butterfly effect. Hitler could have picked many capable officers who were senior to Rommel for the African command. Instead, he happened to pick a relatively junior officer, who turned out to be the best possible choice for the assignment. Hoth was good, but not as bold as Rommel (who was?), and IMO, without Rommel's boldness, the Allies would win the campaign fairly quickly. **
Hoth reaches Africa in February 1941, but waits six weeks for his forces to arrive before attacking the British in Libya. OTL the British have not sent any forces to Greece, and this more than makes up for the reduced shipments around Africa. Hoth's March attack, initially successful, runs out of steam south of Benghazi. British forces under O'Connor push Hoth back to El Agheila in early April.
With no Axis successes in Africa or the Balkans, the Middle East remains quiet. British forces concentrated in Libya attack west in early May; British naval and air forces sink so many Axis supply ships that Hoth's forces collapse and Tripoli falls on 7 June.
All this has had an effect on the thinking of Stalin. He has dismissed all reports of German plans to invade the USSR in 1941 as British provocations. Britain wants to draw the USSR into the war on its side. But he starts to think: if Hitler is not planning to attack the USSR, where is the Wehrmacht? Soviet intelligence reports that most of the Axis troops in Spain are Italian, not German. Very few Germans were sent to Africa. Hitler apparently let Libya fall, rather than send more troops, even though he should have immense reserves sitting idle.
Hitler must be planning something big. It can't be the invasion of Britain, because the RAF has won the Battle of Britain, and Axis surface ships are staying far away from the Channel. It must be the invasion of the USSR. Once he comes to this conclusion, the reports of German deployments in the east become entirely plausible.
On 12 June, Stalin reverses his standing orders of the previous four months. All Soviet forces in the Military Frontiers are to go on alert. Tanks and aircraft are deployed for quick reaction to any attack; fuel supplies are prepped for quick use or quick demolition. Infantry dig trenches and build blockhouses and bunkers; artillery batteries register targets. Thousands of non-combatants are evacuated to the east.
These preparations are still in progress when Axis armies storm across the border from the Baltic to the Black Sea. Soviet resistance is strong, but German skill is better. In fierce battles lasting about two weeks, the Axis forces smash up the Soviet front line and begin to drive east. By the end of July, Soviet forces have lost over a million men killed, wounded, or captured. Axis forces have advanced over 200 kilometers, and are threatening Riga, Smolensk, Kiev, and Odessa. But Axis casualties are mounting too: almost 250,000 men, and thousands of tanks, trucks, and aircraft.
German forces win local victories and take Kiev and Riga in August, but fail in the center against intense Soviet counterattacks. Hitler orders all the panzer forces concentrated in the center for an all out drive on Moscow in September. The Germans win a major victory, taking over 400,000 prisoners and reaching Vyazma before the fall rains set in and mud stops all movement in October.
With Soviet losses exceeding two million men, and German forces only 300 km from Moscow, Hitler proclaims the campaign a complete success. But this is whistling past the graveyard - the USSR was supposed to be completely destroyed, and that's not even close.
When the ground freezes in November, Soviet troops attack the German salient west of Moscow on three sides, expecting to destroy Army Group Center. This proves to be a bit premature. While some German positions are overrun, German skill takes a huge toll of the attackers. Whole Soviet corps and armies are ambushed, cut off, and destroyed. The Soviets lose nearly a million more troops, while driving the Germans back only halfway to Smolensk. Still, Axis losses now are approaching a million men.
When the 1942 spring thaw sets in, the front runs from the Gulf of Riga to east of Smolensk, then south to the Dnieper below Kiev, and along the Dnieper to the Black Sea.
** NOTE: the ATL front is well west of the OTL front at this time. Soviet losses are huge - but only half of OTL's, while Axis losses are double. **
and Turkey joins the Allies around 1942 during Case Blue.
It's now time for Case BLUE, the 1942 summer offensive into Ukraine and Caucasus. However, conditions are substantially different from OTL. They have to be different, because otherwise Turkey would not enter the war.
With Bulgaria and Greece neutral, Turkey is in little danger of Axis invasion. Italy could attack from the Dodecanese, but no one is much afraid of Italy at this point.
How significant will the change be?
In this TL, Turkey's accession to the Allies means that Britiish ships can enter the Black Sea, and sweep it of Axis ships. Then Allied freighters can bring Lend Lease aid directly to Soviet Black Sea ports for immediate delivery to the front line (instead of landing at Abadan in the Persian Gulf for overland transport through Iran, the Caucasus, and southern Russia).
Before that can happen, the Italians in the Dodecanese must be dealt with.
What else has been going on? The Battle of the Atlantic has been very rough for Britain, even rougher than OTL. In one very ugly action in June, the old battleship Ramillies was sunk by
Scharnhorst,
Gneisenau, and
Caio Duilio, after which the 30 ship convoy she was protecting was massacred. This action, which took place 1,200 km SW of the Azores, violates the "neutrality zone" proclaimed by U.S. President Roosevelt. In response, Roosevelt deploys U.S. Navy ships to patrol at 40 West longitude, with orders to "shoot to kill" any Axis warships further west.
Hitler reins in the U-boats and raiders, Britain routes all its shipping west of the 40W line, and British code breakers crack the German Navy's HYDRA Enigma key in July. Losses drop to 'acceptable' levels, but the longer routes strain British shipping to the maximum, and there are additional raider attacks in the area between Greenland, Iceland and Ireland.
** NOTE: this is pretty much what happened in late 1941 OTL, except the re-routing. Allied shipping losses dropped by 2/3 for several months. **
Brazil, happy to make a pro-Allied gesture, sends her old battleships
Minas Gerais and
Sao Paulo to patrol the southern end of the Neutrality Line, starting in September.
Mussolini is frustrated. Africa was a debacle. Aside from a long-range airwar in the Mediterranean, and an army on the eastern front, Italy is doing nothing. The only bright spot in the war has been Italian naval strikes on British shipping. Even there, the Germans claimed the lion's share of the credit for sinking
Ramillies, though (according to her captain) it was
Caio Duilio that did the real damage. He decides to Do Something.
In October, he sends Italy's three modern battleships into the Atlantic with orders to find and sink a British battleship. That's fine with Hitler, who is happy to provide the required oil; what he doesn't know is that the Italians have been ordered to ignore the Neutrality Line.
The Italian naval forces in Spain get copies of German decrypts of BAMS (
Broadcast to
Allied
Merchant
Ships code) traffic. This alerts them to a major northbound convoy from Africa and South America to Britain, escorted by HMS
Malaya, moving just west of the Neutrality Line about 2,500 km north of Brazil. The Italian force moves to intercept.
But instead of the convoy, the Italians run into
Minas Gerais. They mistake her for a British ship, quickly destroy her, then steam home in "triumph".
** NOTE: this is analogous to Mussolini's 1940 invasion of Greece: a foolish and desperate move to win some military glory. **
Mussolini has put his foot very deep into it this time. Brazil immediately declares war on Italy, and then Germany. The U.S. comes very close to its own declaration of war (Italy having effectively violated the Monroe Doctrine), but holds off.
The Pacific War breaks out as OTL. The U.S. immediately declares war on the entire Axis.
Britain, not having an active theater of war in North Africa, has deployed more and better troops in Malaya and Burma.
** NOTE: Especially better. The troops in Malaya OTL were what had been spared from the fighting fronts, and were disproportionately green, ill-equipped, and undermotivated. **
The Malaya campaign lasts twice as long as OTL. By the time Japan invades Burma, the defenses there are relatively solid.
** NOTE: They won't be good. Field Marshal Slim in his memoir noted that the responsibility for Burma's defense changed several times in the previous five years, and that none of the responsible bodies ever seemed to consider that Burma might actually be attacked until the Japanese came over the border. **
They hold until the monsoon comes. But let's forget the Pacific War, we're interested in Europe and North Africa.
With the U.S. in the war, the Allies start thinking about serious counterattacks for the first time. French North Africa is an obvious path to Spain. But nothing can be done for several months till the U.S. can get some troops in the field.
Going back to the Eastern Front. When the ground dries out at the end of spring 1942, the Germans launce Case BLUE, an all out attack into Ukraine, to capture food-growing land and mineral resources. The ultimate goal of BLUE is the oil of the Caucasus - but the Axis never gets there, being stopped on the Don River. Axis troops break into the Crimea, but fail to take Sevastopol.
Per the OP, Turkey is somehow induced to declare war on the Allied side in July 1942. British airpower relocates to southwestern Turkey and beats down Axis air in the Dodecanese in a few weeks. There are artillery battles between the islands and the Turkish coast. British and Turkish troops easily cross from the mainland to the islands in August; all surrender by early September. There are a few air raids on Istanbul from Romania before British planes and radar are flown in.
In September British warships enter the Black Sea and secure it. Lend-Lease materiel is delivered directly into the besieged port of Sevastopol and to Novorossiisk.
Back out west, the Battle of the Atlantic has turned badly against the Allies. U-boats and surface raiders are unleashed on American waters and wreak havoc. The U-boats have a new unbroken Enigma key, and convoys can't evade the patrol lines and ambushes. In addition, the powerful surface forces in Spain pose a potential threat anywhere from Trinidad to Newfoundland. The US is forced to commit the carriers
Wasp and
Saratoga to the Atlantic to cope, especially after
Eagle is sunk and
Formidable damaged by U-boats, and
Ark Royal is crippled by German aircraft.
The commitment pays off in May, though, when
Wasp's planes spot and cripple
Scharnhorst, which is then finished off by
Renown and
Warspite. A further payoff comes in June when
Saratoga sends her dive bombers against the Axis anchorage in Vigo Bay, in coordination with a high level raid by Bomber Command from England. Bomber Command's operation is costly (23 of 80 planes lost) because the target is out of escort range, but it allows Saratoga's bombers to sink the battleship
Giulio Cesare, cruisers
Bolzano,
Monteccucoli, and
Nurnberg, and three German destroyers, plus damage to
Littorio,
Prinz Eugen, and the Spanish cruiser
Canarias. This attack becomes known as the "Fish-in-a-Barrel Raid." The destruction of
Giulio Cesare in a colossal magazine explosion is caught by the gun-camera of a dive bomber, and becomes an iconic image.
Mussolini now panics and orders all his ships back to Italy. Franco is unhappy too. The Vigo raid was the first daylight bomber attack on Spain, something he had been promised would never happen. Also, Spain is suffering acutely from shortages of food and oil. Hitler's promises have proved worth their weight in gold. Franco is viewed as a sucker, having put Spain in a hole for nothing.
In the fall of 1942, things start to go very bad for the Axis.
Pro-Allied sentiment has been growing in French North Africa, both from anti-Axis principle and pure opportunism. Allied forces have massed in Libya, aon the Tunisian border, and in Spanish Sahara, on the Moroccan border. On 12 October, the balloon goes up.
Key French commanders in Morocco announce for the Allies as Allied motorized troops rush north from the border. U.S. troops land at Casablanca unopposed. British troops march unopposed into Tunisia; pro-Allied paramilitaries seize control of Algiers, and British forces land from two fast transports.
Germany responds with aircraft troops, which reach Spanish Morocco by air in two days. By 18 October there is a division and a half there and Axis forces have occupied Oran in Algeria.
Then the next bit of manure hits the fan. German and Soviet forces had fought to exhaustion on the Don River line; the front further north had been quiet for several months. Then on 20 October Soviet forces attacked from Orel to Velikiye Luki. Army Group Center disintegrated, and Soviet forces stormed forward across 400 km of front, with nothing but distance between them and Berlin.
Hitler turned, as he did so often, to Field Marshal Model, "the Fuhrer's Fireman". Model scraped up every reserve, pulled forces from France and Norway, and checked the Soviet advance near Minsk in November. The breakthrough turned the flank of Army Group South as well, which had to fall back from the Don to the Dnieper.
** NOTE: That was Model's OTL nickname. What he did here is what he did OTL in 1944 after BAGRATION. **
The emergency in the east left nothing more to be sent to Africa. Some 250,000 Spanish and Italian troops were ferried over, and the Axis took control of western Algeria and northern Morocco.
The Allies could make little progress on either front, initially, Eighth Army in Algeria was at the end of supply line that stretched all the way around Africa. US Fifth Army in Morocco was mostly green troops; even its British components had only a handful of 1940 veterans.
However, once Allied airbases were established in Morocco, Axis supplies from Spain were substantially interdicted. Allied troops, once blooded, began to batter down Axis resistance with superior numbers and massive firepower. On 15 January 1943, the last Axis troops in Africa surrendered.
Allied bombers from Morocco now attacked Axis bases and communication in Spain. Spanish alienation from the Axis was nearly complete; only a small number of fascist fanatics remained loyal. Nearly all of the tough Moroccan legionaries who had fought so well in the Civil War had been lost in Africa.
On 19 February Franco was deposed and fled to Switzerland, where he issued a bitter screed denouncing Hitler's duplicity. The post-Franco regime immediately approached the Allies to arrange surrender. The Allies demanded unconditional surrender and made no explicit promises; unofficially they agreed to provide Spain with food relief that was urgently needed.
On 15 March Spain announced its surrender. Allied forces took the Balearic islands unopposed and also the port of Cartagena. The main landings on the Andalusian coast met fierce German resistance, but the Allies were too strong and by 18 March the Germans were in full retreat, often harried by left-wing Spaniards who had been suppressed by Franco and now rose up.
On 10 April Allied troops reached Madrid. The Germans finally turned to stand in the mountains south of the Ebro River. On 18 April, Portugal agreed that the Allies could use the port of Lisbon for supplies - and also base ASW forces in the Azores. With that and the loss of Spanish bases, the U-boats were all but shut down till they could set up new bases in France. Even then converging ASW patrols from Spain and England made every deployment and return run a deadly gauntlet.
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I could continue this, but I think I've exhausted the direct consequences and implications of Spanish and Turkish involvement in the war.
Good night all.
