A specially trained soldier armed with an improved shock rifle, rockets, and endurance, they are fierce and dangerous to most that cross their path. They also have decent self-healing to ensure they remain on the battlefield. They are the formiddable midgame boss to many, as they are very effective against ground and air threats. They can only be obtained from deploying Special Forces, which gives 4 S-Marines along with 2 Snipers and 2 Meditecs.
S-Marines carry improved shock rifles for ground-to-ground engagements and improved rockets for ground-to-air ones respectively. Their air capabilities are well known for being highly dangerous to even higher tier air units such as Saints and Phantoms. Their ground weapon is respectable and will eat through Composite armor.
When deployed from a Special Ops team, there are 4 S-Marines alongside 2 Snipers and 2 Meditecs for support. Although the Snipers are more for ground coverage, having 4 S-Marines right away can let them unleash their superior anti-air rockets against Scout and Phantom swarms, and the Meditecs will keep them alive despite the incoming return fire.
Despite wearing light armor and being infantry, their health regeneration, higher health, and backup Meditecs provide them with the help they need to stay alive longer and survive what would decimate normal Marines, such as Chronite Tank shots. S-Marines can tank 1 entire Chronite Tank shot as an example of their durability.
Despite their strengths, they are very vulnerable to Missile damage from both the Black Queen and Special Operations structure. Just 1 from either will kill the entire Special Ops team, leaving nothing behind.
While very effective in the early and mid-game, these units struggle to pack a punch when it comes to the late-game. This is when the more powerful Tier-3 units both shred and are unphased by the weaponry these units offer, such as Hover Tanks, Black Queens, A28-Gladiators, and Sakata Spiders.
S-Marines with proper kiting and micromanagement can be very dangerous effective take down most air threats including Phantoms without dying. It is important to care for them, as they are very important to have around the battlefield and rather fragile if dealing with late-game threats.
It is indeed possible to form a pin with S-Marines, locking any aircraft to be immediately destroyed and being strong enough to tank a Chronite shot and annihilate the tank before it can fire again. Just be wary of Missiles and make sure you have meditecs providing ample healing!