Excellent summary of a long and exhausting war.
My setup was flawed by having the Russians too far west in Poland. As Mike points out, the Germans, with stronger corps, were able to keep me from cutting them off in East Prussia with disastrous results for the Russian army. It was downhill from there for the Russians.
In the previous game, I encouraged the Italians to enter the war early but was not prepared to assist them and Mike wiped them out pretty quickly. In this game, I did nothing to encourage their entry and, once they did show up, moved British and French troops in to stop the evil hordes of Huns and Hungarians from flooding the Po Valley. The Italians held out for two years rather than a few months. TE troops did manage to push into the Alps, but weak supply and heavy CP bombardments made the positions untenable. The German corps in Trent appeared to be invulnerable. I eventually gave up and sought an alternative way into Germany, via Luxembourg, in January 1917. The nice thing about declaring war on the Duchy is that no one gives a hoot.
Most of the TE troops pulled out of Italy with survivors of the aborted Gallipoli campaign moving in to protect Venice. CP attacked Belgium in March but made little headway, thanks to a suicidal attack by a Belgian corps that delayed his attack on Liege. While he did succeed in taking a few Belgian hexes, it was temporary and he was pushed back out. Brave little Belgium held on to the bitter end, even raising another infantry corps (although I am not sure it ever made it into combat). Mike's position on the Western front was strong enough, though, to prevent me from making significant gains and he swept into Italy. The British defenders in Venice were demoralized and, right before the Italians tossed in the towel, I evacuated them, but I had only Athens as a place to send them. I had the idea that they could move up through Greece with the help of cav and, eventually, retake Salonika, but that turned out to be a flawed plan -- Greece, without Salonika, had no rail and the cav that moved to Athens was stuck there, surrounded by rough terrain.
Mike mentions wasting points on tanks but did not elaborate. From my perspective, I saw two tank units show up in Italy. The Italians launched one of their rare offensives and POOF! both tank corps vanished. Seems they are quite weak, at least at the first tech level. Another tank unit showed up later in NW Germany and survived one of my attacks, IIRC, but not a second. I don't recall seeing the tank units ever being in an attack where they may have been helpful to the CP.
As Britain and France ran out of manpower, I found myself in the unenviable position of having lots and lots of economic points but unable to buy much of value except airpower. At one point, I think I had something like 77 air points vs CP's 34.
The US had beaucoup manpower and a treasury with very deep pockets but it could not build more infantry units.
French readiness suffered greatly. Look below at the units. Some of those had not seen combat for a few turns, but still had readiness levels of zero or one.