All online WWI game that has been around for probably 10-15 years now. They've made massive updates to the game though, so the graphics, physics engines, and everything else has evolved and gotten better over time. The map is half scale of Europe and it is probably the most realistic war game ever made.
Entire cities are destructible. Each "game" can last months, although some have been as short as 10 days.
Contains infantry, navy, and air force. Really cool game, I just don't have a good enough PC to play it.