Pick up the anti-tank launcher and go back to where the white guard keeps appearing all the time. By doing this, you should not be in the line of the Yakuza snipers on top of the platform, which is above you. Shoot the helicopter from there. Aim for the men inside the chopper and keep using rockets on it. The rocket man can only hit you if you are closer to him. He cannot damage distant targets. This makes it difficult for the commandos to target you. If you need ammunition, return to the unlimited ammunition cache, However, you can get more ammunition for the rocket launcher if it is low.