Troopers are the shotgun-wielding counterpart to the Lancer. Armed with various shotguns, they lack the accuracy and range of Lancers but are outfitted in more heavily armored yellow attire. This makes them comparatively more effective in close quarters.
Troopers generally share the tactics of Lancers: hide, shoot and throw grenades. However, they often refrain to take cover and move closer to their targets with their shotgun, making them significantly more dangerous in close range.
Troopers will occasionally take cover and blind-fire at their targets, albeit with suffered accuracy; (a) if ever their cover is half of their standing height, almost completely covering most of their weak-spots, (b) if standing near a post or an end of a wall, they will rotate their weapons sideways, hiding most of their bodies until moving sideways reveal them.
They occasionally throw grenades, and when behind cover there is an increased likelihood they will throw one.
On Halloween 2013, they were among the Grineer units whose helmets were replaced by Jack-o'-lanterns.
Prior to Update 11.0 (2013-11-20), Troopers in space-based tilesets used to wield the Strun instead of the Sobek. Until Update 16.6 (2015-05-27) their AIs did not take into account the higher fire rate of the Sobek compared to the Strun, resulting in a very sporadic and slow fire rate. This was fixed in the aforementioned update.
Troopers can spawn with their pre-rework variant (Default helmet, Strun) when the vault alarm is triggered in a Spy mission. They are far more dangerous, given that Struns are also hit-scan and delivers high Impact damage if all pellets make contact.
This, however, is limited to one tileset, notably the same that will also trigger the Lynx to spawn.
Trooper Manually Reloading Some Ammo
Troopers will manually reload some of the shells when initiating a reload, using a separate animation from players. This may be a relic from when the enemy originally used the Strun, and now that players reload the Strun's ammo one shell at a time the Trooper still has trigger to do so as well.
Media[]
Comparison between Troopers in space (left) and Settlement (right)
Trooper in Grineer Settlement with brown camo.
Halloween Trooper after receive a shot with ice mod.
Trooper Codex
Troopers in combat
Grineer Troopers
The old Trooper look within U16 after triggering vault alarms
Hesperia Brown Pigment Farm Dojo Colors (Warframe)
Strun instead of the 
