Meet With Enemy

There are several green trucks that patrol the areas. These are caravans of soldiers. Keep an close eye on them, because running into them means that you'll have to descend and meet with the enemy. When you do hit the enemies, it is both good and bad.

The good thing is it gives you a chance to get the eagle badge bonuses, which allow you to continue.

The bad thing is that you have to fight the more difficult enemies to get them. There are 3 different terrains when you meet the enemy. Marshes, cliffs, and the secret underground passages.

Marshes

The marshes are the easiest of the three combat areas. Fight your way to the end and try to take out the jeeps to get Eagle Badges.

Cliffs

The cliffs have bigger problems. Keep away from the sides, or you'll fall to your death. The rocket soldiers can be found here, so be careful.

Secret Passages

These passages are between areas 14 and 17, and 15 and 18. The bionic soldiers are in these tunnels. Be on your guard here, as there are more soldiers than the other two locations. This is also the place where you can find the helmet.

The weapons that you normally use act slightly different in these areas. Try every gun to see which one you like best. Also, you can use your bionic arm to knock away soldiers and bullets. Make sure you don't forget to use it!