A common topic in alternate history fiction works is what would have happened if a major war had been won by the other side. These usually focus on the events after the war, and the change itself is not depicted realistically: it's either not discussed, or attributed to a superweapon or deus ex machina.
I know that WW1 was a very complex war, with a huge number of social and economic factors in it so that there was no single realistic "miracle" which would have guaranteed a certain different outcome. Therefore I list a number of disclaimers in order to make this question fit into the topic of this site.
- It doesn't have to guarantee an Central Powers victory, but it has to increase its probability significantly.
- A victory doesn't necessarily mean global domination. If Germany ends up with France, Russia, Britain and all the fish in Europe (As would say Bismark of weak countries) as a allied by treaties of peace, so Europe can counter the world domination ambitions of America, it counts as a victory for Germany.
- The change has to be a single event, or a collection of tightly coupled and interdependent events. It has to happen either during the war, or not more than a few years before it. The war should, at least in the beginning, look very similar to what happened in real life: the Triple Entete should be roughly the same, etc.
- The change should have a realistic justification (so no secret Kaiserreich super laser), I would think in the following changes: events progressing slightly faster or slightly slower than in real life, a single large battle or series of interconnected battles won by the opposite side (if that had even a small chance of happening)
- And the new allies of Germany should join the Zollverin.
For acomplish the requiriment number two (2), is required for the European powers to no be broke, or anything that resembles it. And no leftism founding campaings.