This field manual provides a doctrinal framework for the Infantry weapons company assigned to Infantry battalions in an Infantry brigade combat team (IBCT). It is a companion to FM 3-21.10, The Infantry Rifle Company, much of which applies to the Infantry weapons company and as such will not be repeated herein. This manual will discuss on the unique characteristics of the Infantry weapons company, including principles, tactics, techniques, procedures, and terms and symbols. It will also cover what the Infantry weapons company brings to the Infantry battalion and the battlefield. Among topics covered in FM 3-21.10 but omitted here are the characteristics and fundamentals of urban operations, risk management and fratricide avoidance, heavy and Stryker unit employment, sniper employment, improvised explosive devices, operations in a chemical, biological, radiological, and nuclear (CBRN) environment, media considerations, pattern analysis, and situational understanding. It focuses on the employment of the Infantry weapons company while fighting as a pure company or combined arms team under the command of an Infantry weapons company commander. This framework will help Infantry weapons company leaders effectively--Exploit weapons company-unique capabilities; Employ the company using unit weapon fundamentals; Reduce the vulnerability of the unit; Plan and conduct full-spectrum operations; Accomplish missions in various tactical situations, from stability and civil support to high-intensity combat; Win on the battlefield. Although organization for combat may require the detachment of individual weapons company platoons to other units, this manual does not cover detailed operations of detached platoons. It only provides a general discussion of coordination and operational issues pertaining to detachments. The main target audience for this manual includes Infantry weapons company commanders, executive officers, first sergeants, platoon sergeants, and platoon leaders. Others who may find it useful include military instructors, evaluators, training and doctrine developers, and other Infantry company commanders, including those at headquarters and headquarters company and rifle companies; Infantry battalion staff officers; service school instructors; and commissioning source instructors.