I don't think I'd consider Jacobs Ladder a war movie as such,but I do think it's a very good and very underrated movie.Very disturbing at times.
As for movies about war itself,I never watch them any more because there is far too much of the real thing anyway.I watch movies just to get away from the war,ironically.
But a couple of films that sum up the harshness of war are Full Metal Jacket and Gallipoli.But probably the best war movie for me,even though it is told from the "enemy" point of view,is Das Boot.Absoultely gripping and breathless.