Shock troopers or assault troopers 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.
US Army troops getting on a UH-60 military helicopter preparing for air assault training at Nowa Dęba, Poland, 2015
A forlorn hope is a band of soldiers or other combatants chosen to take the vanguard in a military operation, such as a suicidal assault through the kill zone of a defended position, or the first men to climb a scaling ladder against a defended fortification, or a rearguard, to be expended to save a retreating army, where the risk of casualties is high.
Such men were volunteers motivated by the promise of reward or promotion, or men under punishment offered pardon for their offenses, if they survived.
Colin Campbell leading the 'forlorn hope' at the Siege of San Sebastián, 1813. Painting by William Barnes Wollen