Franz-Stefan Gady and Michael Kofman on what Ukraine must do to break through Russian defences

COMBINED-ARMS WARFARE is a deadly ballet choreographed to overwhelm the defender by integrating different combat arms, such as infantry and artillery, and services, such as ground and air forces. Its origins lie in the last two years of the first world war. After years of stalemate, the German Imperial Army adopted innovative tactics to break through the layered Allied defences of the western front and thus out of the attritional deadlock.

This novel approach was not enough to win the war, but it changed the course of warfare. Before 1917 most operations were sequential. Days of artillery fire on a trench gave advance warning of an attack. When the fire paused and infantry went over the top, soldiers would be mown down. The same attack in combined-arms fashion would involve brief artillery fire on the enemy position, combat engineers clearing obstacles such as mines and barbed wire, and soldiers advancing under covering fire immediately afterwards.