Opposition groups today vowed to challenge laws passed overnight that clear Japanese troops to fight abroad for the first time since World War II, saying the changes are a "black stain" on the country's history.
Japan's ruling coalition, led by nationalist Prime Minister Shinzo Abe, pushed the laws through in the early hours of the morning after days of tortuous debate that at points descended into physical scuffles in parliament.
For the first time in 70 years, the new laws will give the government the power to send the military into overseas conflicts to defend allies, even if Japan itself is not under attack.
The nationalist premier argues the laws are necessary to protect against threats from an increasingly belligerent China and unstable North Korea, but opponents fear the vague wording could see Japan dragged into far-flung foreign wars.
Abe has faced bitter opposition over the changes, which have seen his popularity slump, and opposition lawmakers have vowed to do everything in their power to fight them.
"This is not an end," said Renho, a senior lawmaker from the main opposition Democratic Party of Japan, who goes by one name.
"Let's make it the beginning of the beginning," she said on Twitter.
Mizuho Fukushima, a senior lawmaker from the Social Democratic Party, told a crowd of more than ten thousand who gathered outside parliament during the debate: "Abe's cabinet criminals... Let's get them out of here."
Speaking after the vote, Abe said the changes were "necessary in order to protect people's lives and peaceful way of life".
"This is designed to prevent wars," he told journalists.
Abe had been unable to muster support to amend the pacifist constitution and instead opted to "re-interpret" the meaning of self-defence in order to push through the new laws, but the move has sparked a groundswell of opposition not seen for decades in Japan.
A hard-core group of some 300 protesters gathered outside parliament on Saturday, calling for the legislation to be abolished and vowing never to stop their fight against Abe.
"Our battle will never end. This is just the beginning," Keisuke Yamamoto, an organiser from one of the citizen groups that have been leading weeks of rallies, told AFP.
"We will resort to every possible measure, including bringing the case to the courts... We can't let this movement fizzle out now."
Behind him, demonstrators carried banners or billboards, which read: "We should not get children killed," and "Don't let them wage a war".
