A battering ram is a siege engine designed to break open the masonry walls of fortifications or splinter their wooden gates. They prove effective weapons of war because old fashioned wall-building materials such as stone and brick are weak in tension, and therefore prone to cracking when impacted with force. With repeated blows, the cracks would grow steadily until a hole is created. Eventually, a breach would appear in the fabric of the wall—enabling armed attackers to force their way through the gap and engage the inhabitants of the citadel.