Marine (StarCraft)

The marine is the basic infantry unit of terran forces.

The marine is the most versatile tier 1 unit in the game. Compared to the zealot and the zergling, the marine is cheap, is the only one with a ranged attack, and can even hit both ground and air units. They do normal damage, making them useful against all types of armor, and are even more effective in large numbers. StimPacks further increases their effectiveness by greatly increasing their movement speed and reducing their cooldown to almost nothing, at the cost of 10 hit points, enabling marines able to dish out a surprisingly large amount of damage before being killed. In Brood War, medics exponentially increase the effectiveness of marines since StimPacks can be used more liberally, and damage can be healed. Infantry upgrades throughout the game increase the marines' effectiveness by 50%, giving them one of the biggest boosts in the game.

Strategy
Marines are so identified with medics that it's hard to talk about marines without them. Termed "MnM", this unit combination is the core legion of the infantry-focused terran. Deadly and easy to produce in screen-filing numbers, able to shred unprepared armies in seconds, MnM is the dominant terran strategy against zerg.

Needless to say, in any terran infantry game, stimpack should immediately be researched, medics produced, and marine range not far behind. While marine range is not needed to counter any specific units, as compared to dragoon range, it does get marines firing sooner, resulting in a noticeable damage increase. Terran infantry, marines and medics along with tanks and science vessels, are fantastic at holding a ramp or a chokepoint, and defending against air harassment alongside missile turrets. Against zerg, it's standard strategy to use marines and medics almost exclusively into even the late game.

Due to their fast cooldown rate, groups of marines deal out immense amounts of small damage quickly. Units with few hitpoints will usually die before they can even touch a group of marines, particularly if you attack move towards them. Against stronger units, focus firing marines on them will help bring them down faster, before they are able to break your lines.

But marines are also tricky to use because they are so fragile. Attacks that do large amounts of damage can kill marines before they heal, decimating an entire infantry forces in seconds. This makes controlling groups of marines critical and risky, making MnM micro one of the most difficult challenges in the game. To escape these attacks, such as burrowing lurkers or defilers about to attack through dark swarm, stim the marines and immediately move them back out of range. Medics will escape on their own, chasing the marines away trying to heal the stimpack damage. Then you can flank, irradiate the defilers or lurkers, and counterattack when the lurkers unburrow or the swarm disappears. Microing MnM is particularly difficult because only hot keyed marines can be moved fast enough to avoid casualties. This means large groups of marines can need a lot of hot key prepping for these attacks, eating up valuable time. The results can be worth it. Impressive players can make their marines dodge lurker spines, can avoid dark swarm, or split up and surround reavers and tanks.

Early Game
Marines have strategies available throughout the early, mid, and late game. In the early game, a single marine and SCV can start a dreaded bunker rush. If the terran goes supply depot, barracks x2, refinery, and academy, the first medics can assist a very dangerous attack as well. This play is very common against the zerg before mutalisks or lurkers can be produced, with the goal of forcing the opponent to waste money building defensive sunken colonies to prevent off the attack, at no cost to the terran. A siege tank (if you still have time) or additional marines can provide increased pressure against the sunken colonies and threaten a win.

Proxy barracks make these early game strategy faster, riskier, but even more decisive.

If you choose a different early game strategy, marines become your lone defenders. At this critical stage of the game, it takes finesse and confidence to compete against the stronger melee zealots and zerglings, who will quickly kill your small numbers of marines if they can get close.

So keep your marines away! Make opponents waste precious time chasing your marines around. Against zealots in particular, you can run your tiny marines between buildings or through your SCVs line. Many times those fatty zealots get hung up or have to take the long way around, all while you get free shots in before running back to the other side again. Take advantage of the marine's ranged attack, and hide marines in places where those zealots can't reach or zerglings can only approach one at a time. Common places include behind a building block on your ramp, behind 2 hold position SCVs blocking your ramp, or vertically in between your command center and first barracks. Depending on these mazes makes early building placement crucial for terrans. Don't be afraid to practice and watch pro videos to learn how to fight off these early aggressors. The marine's job is to give the terran time to get the tech to force the next phase of the game.

Occasionally you will also see marines use bunkers on the defensive. These bunkers give additional hit points to the marines inside, but are expensive and can only cover a static area. Bunkers are usually used to buy time or cover chokepoints where an attack is guaranteed. Remember that you can't stim marines inside a bunker, so leave them outside the bunker before an attack, and stim and bunker up as soon as the attack hits. Marines inside the bunker are outranged by static defenses like sunken colonies, so careful placement of bunkers is critical. Many games are decided by aggressive zerg sunken colonies placed just out of the range of bunkers, slowly being built into the terran's main as the marines are forced to fall back. If you're feeling foxy, many players when they see a bunker will assume it is full, so by leaving them empty you can sometimes fool the opponent into thinking you have a stronger defensive force then is actually there. Placing bunkers behind supply depots is also a good strategy, sometimes forcing zealots and zerglings to have to walk around a supply depot block to reach a bunker full of marines. Placing another bunker next to the supply depot block and filling it with marines and firebats could also prove very effective against melee enemies, even ultralisks.

Mid-Game
In the mid-game, marines and dropships make incredible harassers, a key part of terran's mobility. A dropship of 6 marines and 2 medics with stim can destroy a base with minimal defenses before the enemy can react, and flee without any casualties. Against the opponent who tries to expand, taking advantage of the terran's typical defensive stance, marines and dropships are the perfect counter. Larger numbers of marines and dropships, if they can safely land, are capable of strong strategic attacks with little threat to the turtling terran, able to outflank the enemy's position and wiping out the enemy's main infrastructure, in multiple locations at once.

Late Game
In late game, epic numbers of marines can easily provide front line defense for tanks and science vessels, particularly in terran vs. zerg matches. Since they produce so quickly and cost only minerals, marines are also fast and cheap reinforcements, allowing terran to stay on the offensive. Marines can aggressively push across the map unless confronted with large numbers of their counter units, or spread out and nip overextending bases in more places then the opponent can react.

Counters
Individually, marines are easy to pick off with almost every other unit in the game, but in larger numbers with medics they are a fearsome, dogged threat. Counter marines with heavily-armored, high hit point units such as battlecruisers and ultralisks, which take little damage from marine attacks. Sunken colonies are similarly effective in numbers of approximately 1:4. Marines are also vulnerable to units that deal splash damage like lurkers, reavers, and siege tanks, and area effect spells like psionic storm. Fast units controlled to execute hit-and-run attacks (Vultures, mutalisks) can pick off marines before they can do much damage. Marines are also much more vulnerable when flanked, when they don't automatically focus fire the same units and can't retreat so easily from threats. Speed upgraded zerglings, hydralisks, and zealots in particular are best used for these sorts of surround attacks against marines and medics. Dark templar are also deadly in flanking marine groups given that they can cut through a marine in only one blow. But, many times, the zerg player has no choice but to use dark swarm and plague to break a chokepoint guarded by marines and tanks. While pushing a MnM force back, keep a careful watch for marine-loaded dropships, and try and destroy the delicate craft before the marines have a chance to land. Irridiation is also fairly effective against clustered marine groups.

On most cases, marines are fair poorly against protoss units given that many protoss units inflict high damage compared to their terran and zerg counterparts.

Against Terran

 * Counters Hard: dropship, missile turret, science vessel, valkyrie
 * Counters Soft: Wraith, SCV
 * Hard Countered by: battlecruiser, irradiate, spider mine, vulture, siege tank (siege mode)
 * Soft Countered by: firebat, goliath

Against Protoss

 * Counters Hard: corsair, shuttle
 * Counters Soft: probe, scout
 * Hard Countered by: archon, carrier, psionic storm, reaver
 * Soft Countered by: disruption web, dragoon, zealot, dark templar, photon cannon

Against Zerg

 * Counters Hard: devourer, overlord, spore colony, scourge
 * Counters Soft: drone, hydralisk, mutalisk, zergling
 * Hard Countered by: guardian, lurker, sunken colony, ultralisk
 * Soft Countered by: dark swarm, ensnare, plague

In the Pro Leagues

 * Boxer, the Emperor, was often considered to be one with his marines. He invented almost all of the techniques which marines known today, and continues to proxy barracks or dropship marine almost every match.
 * Nada

Quotations

 * See: StarCraft I Marine Quotations