how do you destroy the bunkers ?

after shooting the enemy inside the bunker, you will find C4 explosives on the ground (inside the bunker). If you stand close to it and look at it, then a text will appear on your screen. Something like: 'to use C4, press x'. As long as these words are on-screen, you can press x. (so, it does not work if you look up or away). And then you better run like h...!

Thanks progast but my problem is getting to men in the bunkers .you said shoot them, correct? That's it?. I thought maybe the two transport tanks that were at the beginning could be boarded and used to blow up. Okay then I'll just continue to blast away with platoon and rifles. I just didn't want to waste my time trying to get in on foot and realize it couldn't be done. Thanks

That's it. You can't board the vehicles as you probably already found out.
Isn't a game all about wasting your time on various 'wrong ways' until you find a 'right way'?