mock cavalry battle; piggyback fight
A team game, often played at school sports days, where riders on carriers' shoulders try to knock off opponents' hats or headbands.
In the sports day cavalry battle, the red team snatched the white team's caps.
In a piggyback fight, it's hard for the rider and the carrier to coordinate their movements.
Compound of 騎馬 (kiba, 'horse riding') and 戦 (sen, 'battle'), literally 'mounted battle'. The term was applied to the school game because it resembles cavalry combat.