The infantry is the branch of a military force that fights on foot. As the troops who are intended to engage, fight, and defeat the enemy in face-to-face combat, they bear the brunt of warfare and typically suffer the greatest number of casualties. 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 more physically stressful and psychologically demanding than that of any other branch of the combat arms.