Filmed in ten days only six months after the outbreak of hostilities, this film became the first Korean War movie.
Although it looks like there are quite a bit more, there were actually only 25 extras in this picture, playing both American and North Korean soldiers, and all of them were students from UCLA (the battle scenes were shot in Griffith Park).
Right after this film finished shooting, Samuel Fuller was flush with money. During a Christmas party at his house, invited guest Gene Evans was certain he'd get something valuable. He was initially disappointed that all he was given was the steel helmet with a bullet hole in it from the movie. Decades later Arthur Knight staged a retrospective of Fuller's work at USC. Evans was invited to attend as a surprise guest, unknown to Fuller. The two old friends had not seen each other for ten or 15 years at that point. When Evans returned the helmet to Fuller, the director was very touched.and so moved that he couldn't even talk.
In an early scene, Cpl. Thompson identifies himself as a WWII veteran of the 16th Infantry Regiment, 1st Division. That unit is the same one in which director Samuel Fuller served.
According to Gene Evans, about four or five days into shooting, he was told by Lippert Pictures executive Murray Lerner that his work was unsatisfactory and he was going to be fired and paid off with $1000 for work already done. The real reason Lerner wanted to dump Evans is so he could hire Larry Parks, who had just testified before HUAC about his Communist past. Lerner thought they could get the controversial Parks cheaply but never informed Samuel Fuller. The director was angry, got Evans out of the fleabag hotel he was staying in, and moved him into Fuller's house for the rest of the shoot. The picture was finished with Evans, but Fuller posted a sign as big as the stage door: NO PRODUCERS, CO-PRODUCERS, OR EXECUTIVE PRODUCERS ALLOWED.