Despite their sneaky tactics, a ninja would lose in a battle against a Spartan, according to simulations run during season one of Deadliest Warrior. Based on expert historical analysis of the weapons and tactics used by both Spartans and ninjas, the battle between each warrior would be a close one. However, the weapons and armor used by the Spartans would have made it very difficult for a ninja to bring his enemy to defeat.
Historically, Spartans were well armored, which would have rendered most of the ninjas' weaponry and tactics useless, or distractionary at best. Additionally, a Spartan's weaponry was specifically made for slicing through moderately resistant body armor, which as ninjas tended to rely on stealth rather than protective gear, made them particularly vulnerable to a well aimed spear.