Thanks. I wrote this before taking the time to read about the Italian front and the particulars of Caporetto (I wanted it to happen so Malaparte can write his famous pamphlet "Viva Caporetto!" but I guess he is going to write something else). I have edited out references to Italy in order to keep my hands free.
Thus this is here I need the advice of the board's Ludendorff/German experts:
In this TL, given that a) the Eastern front is still active, b) Turkey has just been dealt a few blows by Russia and Britain, c) the US of A and Greece have entered the war pretty much as OTL, what would the German strategic thinking be for late 1917 - early 1918 ?
1) The search for the decisive battle in the West, as OTL Kaizerslacht ? This is of course a bigger gamble than OTL because it means depleting the Eastern front .(This is what I have in mind but I am not sure it could happen earlier than OTL);
2) The search for the decisive battle in the East, as suggested by Merrick ? Again, a huge gamble. From the perspective of my TL this looks great because it provides for an epic and desperate struggle... provided that the German gamble fails and Russia is able, after untold slaughter, to stem the German advance.
3) Option (2), but preceded by a offensive to finish the Romanian front and get Romania out of the war ?
4) Stalling for time, and throwing peace feelers ? (I don't know, seems quite unlikely).
Subsidiary question regarding the Italian front : Italy launched offensives during the spring-summer 1917 (I can always mention them in the next installment). Caporetto was thus executed as a way to prevent Italy's breakthrough. Let's say that Germany is unable to dispatch troops in sufficient numbers to enact Caporetto, but at least enough to prevent a successful Italian offensive in autumn: does this look correct ?
I'm not a WW1 expert, but here's my 2 pfennig:
Coming up with a plan for the Germans in 1917 is hard, because with Russia holding they are rapidly running out of good options. Their allies are failing, their enemies are getting stronger, the supply situation is becoming critical and they have few reserves left.
I'd expect them to hold in place and try to build up reserves in spring-early summer while they wait to see if the U-boats will bring the British down. Remember that the U-boats were meant to be Germany's ace in the hole, the
wunderwaffe that would cripple their most dangerous enemy and outbalance the entry of the Americans. Once the U-boats are seen to have failed, sitting and waiting for the Americans to turn up is clearly hopeless. they have to win and win fast, before the AEF simply swamps them.
That means a big offensive in either the west or the east (or offer peace, but offering peace means both accepting that the war is lost and getting rid of Ludendorff/Hindenburg and probably the Kaiser. I'd expect them to make a peace offer to Russia, based on pre-war borders and don't ask what happens to the Serbs, but that is expected to be rejected and mostly aimed at morale).
In the west, OTL the Nivelle Offensive ran from April-May 1917, resulting in failure, heavy casualties and mutinies in the French Army. There is a potential window for a German offensive here, but they'd need to be transferring troops from the East in the spring, when they still have faith in the U-boats. The British launched a successful attack at Messines in June and kicked off Passchendaele at the end of July. I'd imagine that the ability of the British to launch a major offensive would be enough to convince the High Command that the U-boats weren't going to win the war. OTL, I think all but 3 of the 80-odd German divisions on the Western Front were cycled through the Flanders meatgrinder and by mid-autumn they had essentially no reserves left.
Once Passchendaele kicks off, I don't think the Germans will be in a position to launch a major attack in the West - any fresh troops they get from the East will go to holding the line in Flanders. A summer offensive is possible, aimed at the weakened French post-Nivelle and taking advantage of Russian paralysis post the Petrograd rising. This would require Ludendorff to go all-in on the western front before he knows the outcome of the U-boat campaign. If he tries, I doubt it will end well - he ends up forestalling Passchendaele and all those British troops and shells that OTL went into the Flanders mud are sent to support the French instead. And the British have a lot of reserves and a
lot of shells.
In the East, the Rumanians are an obvious target - OTL Mackensen tried and failed to knock them out in Summer 1917. OTL, the Western Allies were doing all they could to build up the Rumanians because they were the last functioning Allied army in the East as the Russian disintegrated; TTL they are probably more interest in helping the Russians so the Rumanians may be weaker.
The case against targeting the Rumanians is the same as the case against targeting the Italians - even if successful, it doesn't win the war. For the Germans to pull off a victory, they need to occupy Paris and Petrograd - or more generally knock out two of Russia, Britain and France - before summer 1918, when the American will arrive in strength. Fiddling around in Moldova doesn't get them there. However, the Ukraine and its grain production seems to have had a hypnotic effect on the Germans in 1917-18 OTL, so I can see it happening as part of a more general southern offensive towards Kiev. For the Germans this has the advantage that the campaigning season is long than in Livonia and a southern offensive makes maximum use of allied troops to bulk out the overstretched German army. The Austrians will not see this as an advantage, but there's a potential deal - limited German support for Caporetto (8 divisions OTL) in return for offensive support in Galicia. The downside is terrible logistics, and the Russians, if they can hold together, have a lot of space to trade for time.
To land a decisive knock-out on a major enemy, I keep coming back to a Northern offensive aimed at Petrograd. The German army has dominated the Russian in almost every battle since Tannenberg - Gorlice-Tarnow was the one major breakthrough of the war. Even if they weren't clutching at straws, the Germans will look at the Petrograd rising and tell themselves that Russian morale, both military and domestic, is cracking. Will the Russian soldiers even fight for the generals who had their comrades cut down in Petrograd? Even if they do, can they resist an all-out German drive on the capital? And if Petrograd falls, and the Tsar with it. won't everything else, including the Ukraine and Rumania, drop into their laps? The logistics are easier here too - the region is better developed and they can use naval transport in the Baltic. Rationally it's a long shot - 500km to go against everything the Russians have left - but at this point anything is a gamble.