When you get to the tank sitting on the bridge, you can certainly take him on, but you'll lose. Instead ascend the stairs to the right and go around the tank. Once past, run up the right side to flank the machine guns that are suppressing your squad and keeping their heads pinned to the ground. Travel through the bunkers and you'll confront a Hig Armor tank that shows up to try to ruin your day. Just take the Missile Launcher off the handy rack and scrap the armored caddy.
You have to put four D-charges on the consoles inside of each tower in the next part, but keep your eyes open for trouble. There are a few Heavies making the rounds in the area. Once you take out the towers, battle through the enemy defenses and jump on the elevator with Rico. You can forget about taking out the ATACs and run across the bridge to the other side (you'll also see a Helghan symbol on the wall to the left as you enter). Once you are in the courtyard, don't try to go straight up the middle. Instead take the right or left path. The important thing to not forget is that the enemy is really just trying to push you back and you need to always move forward to make it to the next area.
An ATAC will put itself in your squads path in the next part of Killzone 2. Take your handy light machine gun in your hands and turn him into pieces. The ATAC isn't really that hard to beat at this point. Use the Grenade Launcher for battling through to the palace entrance. There is also lots of ammo around for you to use.
Radec Boss
Radec is actually kind of wimpy boss and the challenge he provides is average. However, he can warp around which makes it difficult to target him. Fortunately, like many killers he has the habit of talking too much. Use this against him and listen to his voice to pinpoint his location. Take your time. The more damage you deliver to Radec, the more his ability to stay hidden will decrease and the more damage you can deliver to him. Don't wander too far from Rico, you need his added fire support to take Radec down.
It's necessary to stay on the move to beat Radec, so there's a balance here. You should make sure to reload whenever possible in case Radec decides to rush you with his knife, which he'll do occasionally. Once Radec has received a certain amount of damage, he'll decide to pull back to a far balcony. Stay behind cover when you can and just shoot from distance to finish Radec and once and for all take him down.