U.S. Marines conduct urban breach demolition and explosives training during exercise Fuji Viper 20-2 on Camp Fuji, Japan, Nov. 27, 2019. Fuji Viper is a regularly scheduled training evolution that allows infantry units to maintain their lethality and proficiency in infantry and combined arms tactics. This iteration of the exercise is executed by an activated reserve unit, 1st Battalion, 25th Marine Regiment, currently attached to 4th Marine Regiment, 3rd Marine Division, as part of the unit deployment program.