Why did Crusaders wear crosses on their clothing?

Beginning in 1095, Crusaders wore crosses of cloth on their clothing—specifically on their breasts—to identify themselves as soldiers in Christ’s army.1

This practice was initiated when Pope Urban II exhorted Christians to reclaim the Holy Sepulchre and other venerated sites in the Holy Land. By wearing the cross, participants signaled their commitment to these military and missionary campaigns, which were viewed as a means of redemption and expiation for sins. The term "crusade" itself is derived from the French word crois, meaning "cross," reflecting the central importance of this symbol to the movement.123