Of course Heroes in Hell is extremely silly. How could it be otherwise? It is, after all, directed by Joe D'amato, features a long stock footage flashback and is part of one of the most goofy and cartoon-like of the filone.
The Italian war movie cycle was so often full of the spirit of the boys-own style comic book take on the Second World War with larger-than-life characters, pantomime German baddies, in this case with both Klaus Kinski and Luciano Rossi providing a two-for-the-price-of-one offer, and often a crime caper undercurrent. Heroes in Hell possesses all these things providing the recipe for a fun filled afternoon viewing.
Luciano Rossi gets, by way of contrast to his man-in-crowd or walk-on-and-walk-off character roles, something to say and do this time. Klaus Kinski pops up late in the feature to deliver the kind of role he was capable of performing in his sleep.
Those who like Italian war movies should like this a lot. Others, maybe not so much.