The Britannian Infantry is the division that consisted of conventional foot soldiers. The use of foot-soldiers within the Empire is still fairly unknown after the Invasion of Japan, and only a few instances of them being deployed are shown, usually when a Knightmare would be too large to use. When they are, squads of Honorary Britannians and Britannians are likely to be used, as "grunt work", like hunting down rebels in a ghetto. Britannian foot-soldiers are typically outfitted with assault rifles, pistols, body armour, and helmets with electronic visors. They are well trained and very loyal to the Empire. They were also present during Emperor Lelouch's regime.
When they're not in their armour, army officers and soldiers are seen to be wearing blue uniforms. The barrack dress uniform consist of the grey jump suit and blue uniforms.
The Britannian Combat Armour is considered to be the most advanced in the world. The armour consist of Gray Jumpsuit, Flak Vest, two Pauldron and a Helmet. The helmet is the most technologically-advanced part of the armour, incorporating a communicator, gas mask, and a highly sophisticated combat sensor suite.
The latter function is only shown in Episode 1 of R1, when Suzaku finds the truck containing CC's capsule and Lelouch. The visor zooms in on the capsule as the door opens, then detects and points out Lelouch. This suggests motion detection, but it can also identify an unmoving human.
The armour itself is highly protective, as evidenced by Episode 1 of R1. Suzaku is shot with a handgun at point-blank range, with the gun being shown to be aimed at a gap in the armour between the back plate and his belt. The jumpsuit nevertheless slowed the bullet enough for Suzaku's fob-watch to deflect it with only a cracked face, though the force was still enough to seriously injure him and render him unconscious.
The combat armour worn by the Knights of St. Michael have a red marking on their chests.