Japan has wrestled with constitutional limits on its troops for decades. Prior to the 1990s, Japan refused to participate in international peacekeeping operations or other missions that might draw Japanese troops into a fight. Though formidable, Japan’s armed forces are organized, trained and equipped largely for defensive operations.

Nonetheless, China’s rising military strength and assertiveness, and increasing calls for Japan — still one of world’s richest countries — to participate in international peace and security operations has forced a new look at how and when its forces might be allowed to fight.

Under the U.S.-Japan Security Treaty, American forces are obligated to defend Japan against attack. But Japan’s responsibilities for protecting Americans are less clearly defined. Abe says he wants to tighten security relations with Washington, and argues that failure to help defend American forces when necessary could jeopardize the alliance.

“Imagine a situation where a U.S. warship protecting waters around Japan comes under a missile attack when our Aegis ship is nearby,” Abe told reporters in July. “If we don’t shoot [hostile missiles] down despite our capability [to do so], the American ship will sink and many young lives will be lost. Can we maintain the alliance under such a circumstance?”