Staff Sgt. Zachary Curran, senior drill instructor, Platoon 2110, Company E, 2nd Recruit Training Battalion, leads his recruits in a guided discussion May 1 aboard Marine Corps Recruit Depot San Diego. The role of the senior drill instructor throughout recruit training is to develop recruits into disciplined, physically-fit Marines, but also mold them into Marines with strong moral values. - Staff Sgt. Zachary Curran, senior drill instructor, Platoon 2110, Company E, 2nd Recruit Training Battalion, leads his recruits in a guided discussion May 1 aboard Marine Corps Recruit Depot San Diego. The role of the senior drill instructor throughout recruit training is to develop recruits into disciplined, physically-fit Marines, but also mold them into Marines with strong moral values.