Infantry

Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of the Combat Arms they are the backbone of armies. Infantry units have more physically demanding training than other branches of armies, and place a greater emphasis on discipline, fitness, physical strength and aggression.

Infantrymen are distinguished from soldiers trained to fight in other roles. That is, soldiers trained to fight on horseback, in tanks, or in technical roles such as armourers or signallers, but basic infantry skills are fundamental to the training of any soldier, and soldiers of any branch of an army are expected to serve as auxiliary infantry (e.g., patrolling and security) when necessary. Infantry can access and maneuver terrain inaccessible to vehicles and tanks, and employ infantry support weapons that can provide heavier firepower in the absence of artillery.

Since the end of the Second World War the infantry has become a smaller part of armies of the Western world, constituting typically between 10% and 30% of an army's personnel. Despite still often representing the largest individual arm (with the exception of logistics), this is vastly reduced from pre-war levels. In the United States Army, there are only approximately 49,000 infantrymen out of the millions of soldiers. This reflects the greatly increased requirement for technical and logistical specialists in Western armies, resulting from the increasing complexity of military technology and equipment and an increased recognition of the importance of logistics in warfare. In armies of developing world nations, infantry still accounts for a majority of soldiers, but they are often lacking adequate training in infantry tactics and resources to be as effective as other infantry.