Most infantry master sergeants serve as the operations chief of a weapons company, in place of the gunnery sergeant found in the company headquarters of a rifle company. Infantry master sergeants also serve as the assistant operations chief in the S-3 section of the headquarters of an infantry regiment and Marine Expeditionary Unit and in the G-3 section of the headquarters of a Marine Expeditionary Brigade. The Marine division and Marine Expeditionary Force headquarters contains two infantry master sergeants, one as the training SNCO and the other as the readiness chief.