A new security law which enables Japanese troops to fight in foreign wars for the first time since World War II takes effect on this Tuesday.
The controversial law, backed by Prime Minister Shinzo Abe's ruling coalition, is intended to strengthen Japan's defense against the growing security threat posed by China and North Korea.
The law loosens post-World War II constraints on the use of force by the military to its own self-defense only.
Japan's opposition parties, which were unsuccessful in their attempt to block the legislation last year, say the law is "unconstitutional".
Japan's neighbors, including South Korea, have expressed concern too, given Japan's history of aggression in the region.
Japanese citizens also seem to fear the law could erode Japan's postwar pacifism.
A poll conducted Tokyo-based Kyodo News last weekend found nearly 50 percent of respondents were not in favor.
Just 39 percent viewed the changes in a positive light.
With the ongoing controversy, sources say Abe will postpone assigning new missions to the Self-Defense Forces until after the House of Councilors election this summer.