TOKYO - Japan's parliament has approved legislation that will expand the role of its highly restricted military, opening up the possibility that it could fight abroad for the first time since World War II.
Advocates say the measure, passed Saturday after days of tortuous debate, is vital to ensure Japan can respond to threats from an increasingly belligerent China and unstable North Korea. Opponents argue it will fundamentally alter the country's pacifist character.
Key ally the United States and some Southeast Asian countries have welcomed the move, but China accused Japan of threatening regional peace and said it had failed to learn "profound lessons from history".
The legislation has been something of a pet project for nationalist Prime Minister Shinzo Abe, but has been highly controversial in Japan, and has cost him a lot of public support.
Analysts say the deep unpopularity, and looming legal challenges, could effectively put the reforms on ice.
Here are some key questions and answers about the legislation and its potential impact on Japanese society:
Q: How big is Japan's military, and what are the current restrictions on it? Why is it restricted?
A: Japan's military - the so-called Self Defense Forces - has 227,000 personnel across its army, navy and air force. That is small fry compared to China's 2.33 million and 1.43 million in the US, but more than Britain, Germany and France.
Currently, they can only use force for self-defence if the country or they themselves are directly attacked.
The rule is based on the Japanese constitution, drafted by the US after Japan's defeat in World War II, which bans the "use of force as means of settling international disputes".
Q: How would the new law change this? When would Japan's troops be able to go into battle?
A: The law allows Japanese troops to defend their American counterparts, but also troops of other nations friendly to Japan in situations when "there is a clear danger that Japan's existence is under threat" without the mission.
It will take six months to come into effect, but the government still has to seek parliamentary approval before sending troops on any dangerous overseas missions.
Q: Many countries have far fewer restrictions on their militaries - why is this so controversial in Japan?
A: Bitter memories of the carnage of World War II - including the massive loss of life from two atomic bombs - still shape Japanese society.
Many see the constitution's anti-war clause as a defining aspect of the national character and are proud of their seven decades of pacifism.
Critics, including students, lawyers, academics and young and old alike, have spoken out passionately against the changes.
Q: Opponents say the change will drag Japanese troops into US-led wars in the Middle East. Is that likely?
A: Abe has repeatedly said Japan will not get involved in messy, long-running armed conflicts.
He has also argued the changes would make possible threats, such as North Korea, less likely to attack Japan and help forge even closer ties with the US, which has backed the new laws.
But opponents say the vague wording of the bill could allow for combat missions in the future. They also worry Japan could now be seen as an enemy by those fighting the US.
Those fears were heightened this month when Japan beefed up security across its embassies worldwide after a threat from the Islamic State group, eight months after the jihadists claimed beheading of two Japanese hostages in Syria.
Q: Are there likely to be any legal challenges to the legislation?
A: Yes. Opponents, including dozens of respected legal scholars, say the legislation violates Japan's constitution, which would require a public referendum to change.
Abe's government has so far avoided putting it to a public vote - which he would likely lose - by reinterpreting the meaning of "self defence" to include defending allies and friends.
Opponents of the legislation, including mayors of local cites, have said they would challenge it in the legal system, a slow-moving process that could take years to get a final ruling.
The legislation could also be overturned if the supreme court rules the changes unconstitutional. But the top court can avoid giving a clear verdict on a "highly political issue" such as national security.