This is rightly considered a classic cult movie from the 1970's by the once reliable John Carpenter (who also composed the edgy early synth score). Basically it's a faint mish-mash of other movies, the dialogue is reminiscent of great westerns as a black policeman and a white convict battle against gang members in a Night of The Living Dead re-working. It's also tempting to draw Vietnam allegories (as with many American movies of the mid 1970's and after); the faceless, nameless gang members die in the droves but keep attacking the besieged police station and the lawmen and the lawbreakers, black and white, must unite to defeat them and escape with their lives.
The real joy of this movie, however, is the playing of the two virtually unknown leads, Austin Stoker and the late Darwin Joston. They have a great, almost wry chemistry and use Carpenter's stripped-down witty dialogue to great effect. Because there are no 'stars', there are no real expectations, and the shocks when they come (including the famous ice cream sequence) are more shocking for it.
The representation of women leaves a little to be desired (the two female characters obviously shop at the same sweater store!) but the character Lee shows some inner strength and resolve, and even has time for some kind of upper hand in terms of sexual tension between herself and Joston's Napoleon Wilson.
If you haven't seen this movie I urge you to watch it; in terms of B movies and cult thrillers it's the yardstick in my opinion; simple, stylish, violent, witty and not remotely sentimental.
