I've gone through all 27 pages of threads, and I still haven't been able to find a good answer to this, I'm hoping you guys can help me out. This is mainly a problem for me with ammunition, but it happens a bit with supply as well. Right now my game just rolled into 1915, I'm playing as CP. Easy supply is OFF.
My depots and cities scattered around Germany and AH always seem to have some ammunition available - at the top of the screen it says I have about 1,000. However, I'm really struggling to keep my front line units with firepower; all my corps have 1 or 2 medium artillery, and my armies all have at least one heavy and a scattering of super-heavy and medium. In W. Europe, where there are depots and rail lines all over the place, why is my ammo not getting up to the front? I move my munitions trains back to depots, and they don't even regularly fill up. So I started railing the empty ones all over Germany, and sometimes it still takes multiple turns to fill them up.
I thought supply lines were effectively infinite across rail lines - what do I have to do to keep my dudes supplied? Do I need to upgrade all my depots to level 2 or 3? I doubt I'm producing that much per turn, but since the tooltip for that at the top of the screen doesn't work, I can't be sure. But I just built my first munitions factory last turn.