TBS Phase 3 Exam Questions and Answers 2026 | 100+ Marine Corps Defensive Operations, Fire Support & Combat Engineering Questions | SOSRA, FOCDPIG, Night Attacks, Machine Guns & Movement to Contact

This comprehensive TBS Phase 3 Exam study guide contains more than 100 exam-style questions and verified answers covering the critical tactical, engineering, fire support, machine gun employment, defensive operations, and maneuver warfare concepts taught during Phase 3 of The Basic School (TBS). Designed for Marine Corps officers, officer candidates, NROTC midshipmen, PLC candidates, OCC candidates, infantry leaders, and professional military education students, this resource provides a focused review of the doctrinal knowledge and battlefield planning principles most frequently tested during TBS evaluations. The question-and-answer format reinforces rapid recall of essential concepts while strengthening tactical decision-making and operational planning skills. The guide provides extensive coverage of combat engineering and obstacle integration, including the Battlefield Functions of Engineering: Mobility, Countermobility, Survivability, and General Engineering. Students will review reinforcing obstacle employment principles using the FOCDPIG framework (Covered by Fire, Observed, Concealed, In-Depth, Protected, Integrated, and Non-Geometric), obstacle planning, wire entanglements, protective obstacles, tactical obstacles, and supplementary obstacles. The material explains how engineers shape the battlefield, enhance defensive combat power, and restrict enemy maneuver while preserving friendly freedom of movement. These concepts align closely with Marine Corps engineering doctrine and defensive operations planning. A substantial portion of the document focuses on obstacle breaching and maneuver support operations. Students will master the SOSRA breaching fundamentals—Suppress, Obscure, Secure, Reduce, and Assault—which form the foundation of Marine Corps breaching doctrine. The guide examines how breaching forces integrate direct fires, indirect fires, engineers, maneuver units, and command-and-control systems to penetrate enemy obstacle systems and maintain offensive momentum. These principles are essential for offensive operations and battlefield mobility in complex combat environments. Machine gun employment and fire control measures receive detailed attention throughout the study guide. Topics include General Support, Direct Support, and Attachment relationships, machine gun displacement planning using the MORT framework (Method, Objective, Route, Time), range card development, Final Protective Lines (FPL), Principal Direction of Fire (PDF), target engagement considerations, and defensive fire planning. Students will learn how machine gun units integrate with infantry maneuver elements to provide suppression, security, and sustained combat power across offensive and defensive operations. The material also reviews sustained rates of fire, hot barrel criteria, and employment considerations for the M240B, M2 .50 Caliber Machine Gun, MK-19 Automatic Grenade Launcher, and MK153 SMAW. The document provides comprehensive instruction on offensive and defensive fire support planning. Students will review the four classifications of offensive fires—Fire in Support of Maneuver, Isolation, Assault, and Consolidation—along with the components of an effective Fire Support Plan. Key concepts include fire support tasks, effects, purposes, and methods using the TTLODAC framework (Target, Trigger, Location, Observer, Delivery System, Attack Guidance, and Communications Net). Additional coverage includes Fire Support Planning in the Defense, Long-Range Fires, Close-In Fires, and Final Protective Fires (FPF), emphasizing the synchronization of indirect fires with maneuver operations. Night operations and movement to contact procedures are also covered in detail. Students will examine the three essential elements of a successful night attack—Direction, Control, and Surprise—as well as illuminated and non-illuminated attack techniques. The guide explores Probable Lines of Deployment (PLD), tactical control measures, assault coordination, and battlefield navigation under limited visibility conditions. Movement to Contact (MTC) doctrine is reinforced through discussion of the Approach March formation and the tactical considerations associated with establishing enemy contact and developing the situation. Defensive operations planning is another major area of emphasis. Students will review engagement area development, leader’s reconnaissance priorities, sectors of fire, crew-served weapon placement, LP/OP integration, command post location selection, fire plan sketches, range cards, target reference points (TRPs), trigger lines, early warning devices, and defensive priorities of work. The material explains how Marine leaders organize defensive positions, integrate fires and obstacles, and establish layered security to disrupt, delay, and destroy enemy attacks. These concepts are central to successful defense-in-depth operations and small-unit tactical leadership. The content aligns closely with official Marine Corps doctrinal publications and professional military education references, including MCDP 1 Warfighting, MCDP 1-0 Marine Corps Operations, MCWP 3-1 Offensive and Defensive Tactics, MCWP 3-15.1 Machine Guns and Machine Gun Gunnery, MCWP 3-17 Engineering Operations, Marine Corps Fire Support Doctrine, and Marine Corps Breaching Operations guidance. These references establish the doctrinal framework for tactical planning, combat engineering, machine gun employment, fire support coordination, maneuver warfare, and officer development throughout the Marine Corps. This document is highly relevant for TBS students, Marine Corps officers, officer candidates, infantry officers, weapons platoon commanders, machine gun section leaders, combat engineers, fire support coordinators, NROTC midshipmen, PLC candidates, OCC candidates, military academy students, and professional military education participants preparing for TBS Phase 3 examinations, leadership assessments, officer qualification programs, promotion boards, or advanced tactical training. It is particularly valuable for individuals seeking a comprehensive review of obstacle integration, breaching doctrine, machine gun employment, defensive planning, fire support coordination, night attacks, and Marine Corps maneuver warfare principles. Keywords TBS Phase 3, TBS exam questions, The Basic School, Marine Corps tactics, combat engineering, battlefield engineering, FOCDPIG, reinforcing obstacles, obstacle employment, protective obstacles, tactical obstacles, supplementary obstacles, wire entanglements, mobility operations, countermobility, survivability operations, general engineering, SOSRA, obstacle breaching, breaching operations, machine gun employment, general support machine gun, direct support machine gun, machine gun attachment, MORT, range card development, PDF, principal direction of fire, FPL, final protective line, fire support planning, TTLODAC, offensive fires, fire in support of maneuver, fire in support of isolation, fire in support of assault, fire in support of consolidation, engagement area development, defensive operations, leader's reconnaissance, LP OP, sectors of fire, command post placement, TRPs, trigger lines, early warning devices, night attack, direction control surprise, PLD, movement to contact, approach march, M240B, M2 machine gun, MK19 grenade launcher, MK153 SMAW, Marine Corps doctrine, maneuver warfare, United States Marine Corps