I would argue that this is the best war movie around, followed closely by Peter Weir's Gallipoli.
Peckinpah is such a brilliant director, and so much more subtle than is immediately obvious.
By chosing Germans and Russians as protagonists, classical bad guys, the viewer does not really root for any side. He also chooses Crimea 1943 as the setting. Therefore we enter the film with very few preconceptions.
To add gravity to his message he does not use typical war music in his score; he mixes it with children's rhymes!
The soldiers on both sides are just soldiers, not particularly bad, not particularly good. They are rather portrayed as beeing trapped in a game played by the people behind the front. Most just try to survive, the only exception is the German front line commander who still clings to the, more decent, values of a bygone era.
Even the "bad guy" is not really a typical film "bad guy". He is weak and egotistic, he does not want to be at the front, he does not want this war. In the end sergeant Steiner ackowledges that
and gives him a chance to redeem himself ('Take this submachine-gun and win your iron cross like a man.').
Where Peckinpah's other films are hyperrealistic this one has a more dreamlike (nightmarish!) character. The Russian tanks have a quality of angels of vengeance, and the devastation after the battles are more reminiscent of Brueghel's visions of hell than of the "great day out for the lads" type vision we have from the usual Hollywood fare.
This is great action, but it has a very strong anti-war message. I think that people who only want to see a war movie will feel oddly disturbed after watching it. I think that is the reason for some negative reviews.