Low ranking foot soldiers are the most common enemy that you will encounter. They comprise a majority of the enemy forces, and they are extremely simple minded. They will run towards you in whichever direction they started running, and will continue to run in that direction even if they have passed you. Some foot soldiers are given weapons to attack you with. They may carry shoulder mounted bazookas, or they might be manning grenade launchers.
NES Note: Enemies change in appearance and outfits from one stage to the next. Therefore, their behavior or function is better determined by the color of their outfit. Normal foot soldiers frequently appear in brown or maroon colors.
Gun soldiers appear more frequently from behind than ahead. They run just slightly faster than you, and will attempt to catch up to you just enough to stop and fire off a bullet before they scroll off the screen. If you do not hesitate, they will typically disappear before they have that chance, but be prepared to duck down and let the bullet whiz over your head. If they are still on the screen when they finish firing, they will resume their chase of you. Gun soldiers will typically follow you up or down ladders to alternate elevations, so don't presume you got away just because you changed levels.
NES Note: Gun soldiers on the NES conversion do not tote large firing rifles, but rather pistols. They appear in yellowish colours, and can just run fast, unlike slow supply runners.
Supply runners are not combatants. They are used to provide the soldiers with weaponry which is presumably intended to stop you from succeeding in your mission. However, if you get to the supply runners, you can make use of the weapons that they carry. Since supply runners are not trained for combat, they initially appear lying flat on the ground, attempting to avoid harm. When they see that you are getting close, and they have no choice, they will rise up and begin to jog toward you. This is your opportunity to strike and collect what they have. It may be a flame thrower, a rocket launcher, or grenades.
NES Note: Supply runners typically wear an orange color, or some similar bright color that helps them stand out. They are easily identifiable due to their tenancy to lie flat on the ground. They carry rocket launchers, grenades, invincibility stars, or pistols. However, they will not drop these weapons if you kill them with another. Read the special weapons section for more information about the differences between the American version and the Japanese version of the NES game.
Combat specialists are trained martial artists. They do not behave much differently than regular foot soldiers, but shortly before they would collide with you, they initiate a jump kick. They time this kick with deadly proficiency, and you must react accordingly in order to stay alive. You can anticipate their attack and jump in the air to attack them at the same height, or you can crouch down and let them jump over you. In some instances, if you run forward and do not hesitate, they may jump clear over your head.
Combat specialists are also seen parachuting down from the sky on occasion. As they float down, they will drop some small explosives.
NES Note: Combat specialists are easily identified by the light red color they wear on every stage. These are the most important soldiers to identify so that you can anticipate their attack.
German Shepherds will only appear at the very end of the Harbor stage. Several of them appear at once, lead by a dog trainer. In order to defeat them, you'll need to crouch down low and slash them with your machete before they reach you and bite. You'll have to defeat a few groups of them before you are allowed to advance to the next stage.
Land mines are a relatively minor threat, as they are motionless, and generally highly visible. You must simply ensure that you jump over them, or take an alternate route around them. Stepping anywhere near the vicinity of the mine will cause it to detonate, and you will lose a life.
Famicom Note: In stages 2, 4 and 5, some of the landmines can be blown up to find hidden ladders below.
Gyrocopters are manned by specially trained soldiers. They only appear by the bridge at the end of the Airshed stage. These pilots have the ability to drop grenades upon intruders down below. The pilots will hover the gyrocopters some distance above the ground, and occasionally swoop down low in an effort to mow you down. This is you opportunity to jump up and strike at the copters, disrupting their flight and causing them to explode. It only takes one hit to bring them down, but you must carefully wait for the opportunity to arise.
The Flame Thrower is the ultimate guard of the POWs at the end of the Warehouse stage of the arcade version (he does not appear in the NES version). Just like when you possess a flame thrower weapon, this soldier is capable of firing a jet of flame that will stretch across nearly the entire screen. It does travel quite fast, meaning you will have ample opportunity to leap over the flame and get close to the Flame Thrower so that you can take him out and prevent him from firing upon you again. After dispatching a few of these, you will be able to rescue the POWs and advance to the next level of difficulty.