What follows below is an open letter to Donald Sensing, concerning his disdain for French taxicabs and the outcome of the First World War.
I loved your essay on French taxicabs. While I never looked at how the Germans might have invested Paris (John Keegan argued in The First World War that the Schlieffen Plan couldn't have worked, because there was simply no way on the French and Belgian road systems to move the additional corps into position in time. Schlieffen fudged the schedule for the siege of Paris.), I have given some thought to what an Imperial German victory would have looked like.
We know from the German archives that bits of the Belgian frontier, and the Metz and other French border towns would have been annexed outright. Belgium (and eventually, Holland) was to be made a client state. The eastern French Channel coast would have been, if not Reich territory, then certainly under the control of the Kaiser's army and navy. France was also to be punished with war debts to dwarf those of 1871, and probably on the scale of what happened to the Germans at Versailles in 1919.
And that's just the Western Front.
We know what for certain what Germany would have done in the east, because they did do it, however temporarily, in the Brest-Litovsk treaties. Lithuania -- annexed. The few remaining choice bits of Poland -- annexed. What was left of Russian Poland -- a client state. Moldavia -- annexed. Crimea -- annexed. Georgia -- a client state. Greater Ukraine and Byelorussia to be placed under German princes.
Germany would have had her dream of lebensraum in the east, and (Lesser?) Russia left in the chaos of White-on-Bolshevik-on-Menshevik civil war. Absent firm Soviet control, Japan would surely have held on to Vladivostok and Russia's Far Eastern Maritime Province. The two were enemies in the real Great War, but that didn't stop them from allying in 1936. Surely, they would have still found reason to ally in this alternate scenario, if only to keep the Russians down.
In the Balkans, Austria-Hungary would have survived, enlarged-but-diminished. They'd have had a more democratic government, in an ethnic-federal system. A Triple (Constitutional) Monarchy, of German, Hungarians, and Slavs. The Roumanians, practical as ever, would have accepted the new system. The Greeks and Serbs wouldn't be happy, and would keep on fighting -- but alternate history can only change so many things (grin).
The Ottomans? Who knows? Europe's Sick Man would still stay sick, but with German soldiers and bureaucrats, they might have held on to their Arab lands de jure, while Berlin ruled them de facto. No Balfour Declaration, no Israel, and Germany with at least 20% of today's known oil reserves.
In the West? A triumphant Imperial Germany, with the coal and steel of the Low Countries, an enlarged (and thus more easily violated) border with an impoverished France, the Channel ports from which to directly threaten Great Britain.
The situation in 1915 Europe would have been 1942 all over again, but with one important difference: The United States would never have gotten involved, never mobilized, and never had the opportunity to get used to the idea of acting like a Great Power.
The good news is, we would have been spared most of Lenin, all of Stalin, and the Holocaust.
The bad news is, there would still have been a Second World War. There would have had to be. The US and Great Britain simply cannot tolerate (as I'm sure you know) Europe under the control of a single, powerful regime. A united, hostile, powerful Europe was Britain's rationale for fighting the Napoleonic Wars, and part of America's reason for sticking around for the Cold War. And that's exactly what Germany, victorious in 1914 or '15, would have had.
How that war would have played out, I have no idea. Our Pacific War with Japan was going to happen no matter who won The Great War -- so perhaps Japan's ambition for more fighting would ignite the Kaiser's, too. What I do know is that Imperial Germany would have been in a much better position to fight it than Nazi Germany was -- and that's a scary thought.