Usually, at least in the case of nuclear weapons, more missiles aren't used but more warheads, with the vast majority being decoys. The way the missiles work i

Usually, at least in the case of nuclear weapons, more missiles aren't used but more warheads, with the vast majority being decoys. The way the missiles work is that they break apart once they reach a certain point in the trajectory, making tracking far more difficult. It's the fundamental difference between adding more target tracking and handling capability to an anti-missile system (expensive) to just throwing out more cheap decoys. This has been an opposition to missile defense systems since the early 1980s when they were first introduced and I haven't read about any system that overcomes this weakness.