For thousands of years, armies moved no faster than a tired soldier could walk
Through most of history, an army's speed was capped by human legs. Even with pack animals hauling supplies, a force could rarely cover more than about 32 kilometres a day unless it travelled by river. Only cavalry or specially trained light troops outpaced that limit, and it held until tanks appeared late in the First World War.
Even then, the change was gradual. Real freedom of movement on the battlefield arrived only in the Second World War, when armoured and motorised formations won striking victories. Yet much of every army in that war still depended on horse-drawn wagons, which held back the whole. Engineers could also slow any force by building obstacles in its path.
Tactics are often analysed as a balancing act between four functions: firepower, mobility, protection and shock. Shock is partly in the mind. At Agincourt in 1415, clouds of English arrows sent the French knights' horses into panic, and in both early modern warfare and the opening years of the Second World War, the psychological blow of an attack often exceeded the casualties it caused. Protection swings too: body armour was largely abandoned by the 18th and 19th centuries, then helmets returned in the First World War to guard against artillery.
Firepower's rise was not purely European. Massed volleys by Japanese archers made infantry firepower prominent in the later 13th century, before the English longbow's heyday. Cavalry could still triumph, as the Oirat Mongols showed at the Battle of Tumu in 1449, but gunpowder steadily tilted things toward foot soldiers, exemplified by massed arquebus fire at Nagashino in 1575. The military thinker J. F. C. Fuller divided Western warfare into a shock cycle from 650 to 1450, a mixed era to 1850, then a projectile age.
Air power reshaped the picture from 1918 onward, even allowing armies to be supplied from the sky. The British managed it in Burma, while the Germans failed at Stalingrad. Troops landed by parachute or glider, however, arrive lightly armed and slow on the ground, a weakness exposed during Operation Market Garden in September 1944.
Source: Military tactics
