I struggle with his argument because it bases itself on the certainty of "it didn't happen, therefore it couldn't happen" and fails to take into account that even a minute change at the time could have resulted in an entirely different outcome.
Had Jackson not died at Chancellorsville or Buford not engaged Confederate forces at Gettysburg, had the Italians and Romanians put up a better fight at Stalingrad things may have ended differently.
Basically it is the Butterfly Effect, it is impossible to determine its effect but fun to postulate.
Russia fans seem to like pushing the idea that it is Ukrainians who started this yet none of it would have happened had Russia not crossed the border in 2014, they generally get very upset at pushing black and white arguments back at them.
Strangely I enjoy US Civil war discussion even when I don't know much about it as I find it fascinating.
NO : you fail to take in account the fact that there are always TWO , not ONE, sides in a war .
Napoleon won battles but lost the war .
Jackson won battles but the South lost .
German capture of Stalingrad would still result in the German defeat .
Wars are not decided by battles .