Shock troops or assault troops are formations created to lead an attack. They are often better trained and equipped than other infantry and expected to take heavy casualties even in successful operations.
"Shock troop" is a calque, a loose translation of the German word Stoßtrupp. Assault troops are typically organized for mobility with the intention that they will penetrate enemy defenses and attack into the enemy's vulnerable rear areas. Any specialized, elite unit formed to fight an engagement via overwhelming assault (usually) would be considered shock troops, as opposed to "special forces" or commando-style units (intended mostly for covert operations). However, both types of units could fight behind enemy lines, by surprise if required.
Although the term "shock troops" became popular in the 20th century, the concept is not new, and Western European armies in past centuries called them the forlorn hope. Presently, the term is rarely used, as the strategic concepts behind it have become standard contemporary military thinking.
Before 1914
In 375 BC, under the command of the younger Pelopidas, the Theban Sacred Band was united as a single unit of shock troops. Their main function was to cripple the enemy by engaging and killing their best men and leaders in battle.
The Companion cavalry of Alexander the Great (356-326 BC) are described as being the first example of shock cavalry being used in Europe.
Several sources describe how the Vikings used Berserkers as shock troops in organized warfare.
During the Crusader period, the various Catholic military orders such as the Knights Hospitaller, Knights Templar and the Teutonic Order were considered shock troops.
The Shorn Ones were the most prestigious warrior society in the Aztec Empire, serving as its shock troops.
In late-medieval Europe, the German Landsknecht and Swiss mercenaries used large Zweihänder swords to break into pike formations. Polish Winged Hussars, elite heavy cavalry used by the Polish–Lithuanian Commonwealth, have also been described as shock troops. The Ottoman Army used Deli as shock troops as well.
Grenadiers originated as specialized assault soldiers for siege operations. First established with a distinct role in the mid- to late-17th century, grenadier units would throw grenades and storm breaches, while leading the forefront of a breakthrough. Even after abandoning the use of the original black-powder grenade, armies retained the grenadier companies and regiments as specialist assault troops.
The armies of both the Union and the Confederate States in the U.S. Civil War each fielded several crack infantry units used as shock troops. The Union's Army of the Potomac utilized the Iron Brigade and the Irish Brigade (Union Army) in the role, and the Confederate Army of Northern Virginia used the Texas Brigade and the Stonewall Brigade much the same, with all these units suffering high casualties due to the assignments they drew from higher because of their fighting prowess.
During the Paraguayan War (1864–1870), in which Paraguay fought against Brazil, Argentina, and Uruguay, the Paraguayans deployed shock troops (composed of a mixture of dismounted cavalry and fit men who could row and swim) armed with sabres, cutlasses, knives, bayonets, pistols, and hand grenades. They attacked small fortified positions and boarded Brazilian river steamers.
World War I
During the First World War, many combatants faced the deadlock of trench warfare. On the Western Front in 1915, the Germans formed a specialized unit called the Rohr Battalion to develop assault tactics. During the Brusilov Offensive of 1916, the Russian general Aleksei Brusilov developed and implemented the idea of shock troops to attack weak points along the Austrian lines to affect a breakthrough, which the main Russian Army could then exploit. The Russian Army had also formed hunter commando units in 1886 and used them in World War I to protect against ambushes, to perform reconnaissance and for low-intensity fights in no-man's-land.