After a lengthy voyage across the Pacific and around Cape Horn, the ninja arrived in the United States in early 1864. They were swiftly sent to the far west for anti-bushwhacking efforts, targeting Quantrill's Raiders and "Bloody Bill" Anderson's gang that notably included Frank and Jesse James. However, their makibishi caltrops, shuriken, and cane swords were no match for the rifles and revolvers of Confederate guerrillas. Led by Union officer A.V.E. Johnston, the ninja detachment was attacked by Anderson at the Battle of Centralia and killed almost to a man. Their captain, master ninja Tamura Tatsui, was tortured to death over several days by being fed only milk until he finally choked to death. As an outlaw, Jesse James enjoyed flaunting the seven scalps he collected from slain ninja after the battle.

https://en.wikipedia.org/wiki/Union_1st_Ninja_Regiment

(http://www.autoadmit.com/thread.php?thread_id=3984991&forum_id=2#36120182)