soldier, private, troops, army, warfare, strategy, tactics
兵 centers on military personnel and organized fighting: a soldier, troops, or an army, and by extension the warfare, strategy, and tactics they carry out.
兵 originally depicted two hands holding a weapon, later simplified to the modern form with 丘 (axe-like shape) above 八 (two hands). It represents a soldier or military action.
The top 丘 looks like an axe or weapon, and the bottom 八 resembles two hands gripping it. Picture a soldier holding a weapon ready for battle.
For ヘイ, imagine a soldier shouting 'Hey!' as they charge into battle: Hey -> ヘイ, and the soldier's cry echoes across the troops.
arms; weapon; ordnance
(common) soldier; rank and file
soldier
nuclear weapon
armed forces; military; troops
conscription; (military) draft; (compulsory) enlistment
military force; force of arms; strength of an army
infantry; infantryman; foot soldier
military service; conscription
militia; militiaman
cavalry; cavalryman; trooper
dispatch of troops
barracks
artillery; gunner
ambush; troops in ambush
(army) provisions; food
military strength; military personnel
combat engineer; military engineer; combat engineering; military engineering
officers and men
armed forces; battle troops
chemical weapon
withdrawal of troops
Marine Corps; Royal Marines