Infantry is the general branch of an army that engages in military combat on foot. As the troops who engage with the enemy in close-ranged combat, infantry units bear the largest brunt of warfare and typically suffer the greatest number of casualties during a military campaign. Historically, as the oldest branch of the combat arms, the infantry are the tip of the spear of a modern army, and continually undergo training that is typically more physically stressful and psychologically demanding than that of any other branch of the combat arms. Common representations of infantry fighting forces include the U.S. Army Infantry Branch, U.S. Marine Corps Infantry, Royal Canadian Infantry Corps, Infantry of the British Army, and the Royal Australian Corps of Infantry.