Corporal William Wemms
Corporal William Wemms was the non-commissioned officer who lead the soldiers of the 29th Regiment Hugh Montgomery, John Carroll, James Hartigan, William McCauley, William Warren and Matthew Kilroy arriving to help Hugh White when he became surrounded by the crowd.
It helps to understand that in the British army, a non-commissioned officer (e.g. Sergeant or Corporal) is the rank above a solder but below a commissioned officer (Lieutenant and up). Non-commissioned officers are often referred to as "the backbone" of the armed services because of their role as the most visible leaders to the bulk of service personnel. And this is exactly why Captain Preston decided to rely on Wemms to try rescue White.
When Preston made his decision to send a guard to assist White, the first officer to help was Lieutenant James Basset who had arrived from his quarters by this time, but he was of no use whatsoever, continually asking Preston what to do. Preston then called out a guard under Corporal William Wemms and ordered them to fall out in front of the Main Guard before proceeding down the street to the Customs House.
The six privates called out were all Royal Grenadiers, impressive because of their tall bearskin hats. They were William McCauley, Matthew Kilroy, Hugh Montgomery, William Warren, John Carrol and James Hartigan. Unfortunately three of these soldiers have been among the men involved in the ropewalks brawl with Attucks, Gray and rope-makers on the preceding Friday. In retrospective this situation was hardly avoidable, because in the months preceding the Boston Massacre British regulars and local were involved in fights almost daily. In fact on that very night Captain John Goldfinch whose unpaid bill ignited the quarrel between White and Garrick, was called to the British Army barracks to break yet another fight with locals.
During the Boston Massacre trial, Corporal William Wemms was accused together with Captain Preston of ordering the soldiers to shoot unarmed civilians. Both Wemms and Preston were quitted of the charges.