On 18, September 2015, the National Diet enacted the 2015 Japanese military legislation, a series of laws that allow Japan's Self-Defense Forces to collective self-defense of allies in combat for the first time under its constitution. The Self-Defense Forces may provide material support to allies engaged in combat internationally. It also allows JSDF troops to defend weapons platforms of foreign countries that contribute to Japan's defense. The justification is that by not defending/supporting an ally, it would weaken alliances and endanger Japan. These were Japan's broadest changes to its defense laws since World War II.