Most of the time, when movies or video games depict zombies, they are given one crucial weakness; the head. Blow it off, and you stop the zombie.
The United States Army is well equipped to fight the foes which it finds itself against. A shot at center mass from 5.56 or 7.62 round will nearly always put a foe out of a fight- provided they are human.
However, how do they fare against something which lacks nearly none of our squishy, organ-based weaknesses?
In this scenario, zombies are immune (Or at least, heavily resilient) to practically all damage barring the loss of all mobility (Limbs), or complete destruction. Blow ones head off, it will continue to stumble forward to where it last saw you. Cut one in half, it will keep dragging itself forward. Set it on fire, it will continue to run at you, on fire now. Blow a hole the size of a basketball in it... you get the point. Even if you destroy it until its only an arm, that arm will keep crawling at you, until damaged to the point of immobility.
How does the US Army, particularly on a small arms basis, defeat these incredibly tough, unstopping zombies?
Additional factors regarding the zombies:
- They are roughly 2.5x stronger than they would be as a human, their bodies lacking the restrictions which stop the muscles from overworking and damaging themselves
- They are capable of moving at a speed equivalent to a jog, which they can keep up indefinitely.
- They continually move around, and are attracted to sound, light, and human smell.
- If they kill someone, that person is also an infected. If they see a body which died of non-infected causes, they can infect and reanimate it.
- Initial infection is in New York (City), with an initial estimate of infected at 1-1.5 million, which will continue to spread. Some of these are underground.
- Poison gas is ineffective
- Broken bones, a bullet hole in their knee, or limb injuries which would otherwise immobilise a human don't stop them. Utter destruction of the limb, or its removal, are the only certainities.
Note: When I say necromorph-like, I mean in the sense they can only be put down by dismemberment and enormous trauma. They aren't capable of forming giant disgusting flesh monsters, nor are they being controlled by some malevolent Lovecraftian entity.