Members of this unit were involved in a skirmish at Pawas, Pakistan, Earth during the Battle of Earth that year. A team from 3/1 Bravo was assigned to "recover" John-117 by sighting his approach vector as he landed on Earth after arriving on the Forerunner ship. The team, consisting of at least three Marines and a Corpsman, came under heavy attack from a column of Jiralhanae with air support from Banshees and Phantoms, however they were able to successfully hold off the enemy with the help of two ODSTs from Delta Team of 3rd Unit, 2nd Shock Troops Battalion. Though successful, the unit suffered at least one killed and two wounded during the fight.
The unit is mentioned whilst Delta Team head to Sector Six, they are reportedly under heavy fire.
As Delta Team arrive, 3/1 Bravo's members, which consisted of Scottlee, R. Coney and two other unnamed marines, are in a defensive retreat. Coney is called to assist Rymann with Hartley's spiker wound, all the while the marines take cover behind opposite concrete barriers. There is a brief lul in the fighting.
Hartley then instructs the three marines to hold their position whilst he uses their sniper rifle to pin down reinforcements, but he is soon crushed by a Chieftain when ambushed.
As their ammunition supply begins to run low, one trooper makes a dash for the turret of the Warthog Rymann and Hartley arrived in. He manages to shoot two Jiralhanae but takes a spiker to the chest in turn. Coney runs over to him only to accounce he is dead. Scottlee, firing from the rear now, pours on fire but takes an accurately placed spiker round to the left arm; he uses his right to kill the Jiralhanae that shot him.
Hartley then targets John's IFF tag as he comes in on the smouldering remains of part of the Forerunner dreadnought. Coney cuts Scottlee free with an angle grinder and Oscar 6 tells the team to fall back. The last standing marine calls out the retreat but is nearly killed by a Banshee bomb sending him onto the Warthog's windshield. He recovers as Scottlee is cut free and all marines fall back into the bunker, one of which finishes off the approaching Jiralhanae Chieftain with a Rocket Launcher, ending the battle as the bunker doors close.
It is not completely clear what "3/1 Bravo" stands for in terms of unit identification code. 3/1 Bravo could refer to Bravo Company of the 3rd Battalion, 1st Marines (Thus the unit would then belong to the 1st Marine Regiment.) However, the designation could also be far more specific, referring to Bravo team, first squad of the third platoon of an unnamed Company or higher organization. Unit designation codes have been used often in Halo but rarely enumerated upon. See UNSC Military Organization for further details.