For more than seven decades, the international community has grappled with the threat of nuclear weapons. At the United Nations on Friday, July 7th, the vast majority of the world’s governments made clear their total rejection of these abhorrent devices, concluding a treaty to prohibit them, categorically, for all time. It was a moment of great historical significance.

Prolonged applause broke out as the president of the negotiating conference, Costa Rican ambassador Elayne Whyte Gomez, gavelled through the landmark accord. “We have managed to sow the first seeds of a world free of nuclear weapons,” she said. Diplomats and campaigners who had worked tirelessly over many years to make the treaty a reality embraced in celebration of the extraordinary achievement.

Setsuko Thurlow, a survivor of the atomic bombing of Hiroshima and long-time champion of disarmament, became overwhelmed with emotion as she welcomed the formal adoption of the treaty, backed by 122 nations. She asked delegates to pause to feel the witness of those who perished in 1945 or died later from radiation-related illnesses. She was a 13-year-old schoolgirl when hell descended on earth.

“Each person who died had a name. Each person was loved by someone,” she told the crowded conference room. “I’ve been waiting for this day for seven decades, and I am overjoyed that it has finally arrived. This is the beginning of the end of nuclear weapons.” She urged nations never to return to the failed policy of nuclear deterrence, and never to return to funding nuclear violence instead of meeting human needs.

The treaty recognizes the harm suffered both from nuclear weapons use and the two-thousand-plus nuclear test explosions that have been conducted across the globe since 1945. It obliges nations to provide assistance to the victims of these heinous acts. Its overriding mission, as reflected in the preamble, is to ensure that no one else ever suffers as they have.

Abacca Anjain-Maddison, from the Marshall Islands—a Pacific nation devastated by US nuclear testing in the 1940s and 1950s—delivered a powerful closing statement on behalf of the International Campaign to Abolish Nuclear Weapons, whose 400 non-governmental organizations in 100 nations worked for more than a decade to bring about the treaty.

“The adoption of this landmark agreement today fills us with hope that the mistakes of the past will never be repeated,” she said, emphasizing the special meaning that it has for those who have suffered nuclear harm. “The international community has at last acknowledged what we have always known: that nuclear weapons are abhorrent and immoral.”

Governments, too, delivered impassioned statements in celebration of the treaty’s adoption. Among them was South Africa, which played a pivotal role during the negotiations and is the only nation to have built a nuclear arsenal before eliminating it completely. “Working hand in hand with civil society, [we] took an extraordinary step [today] to save humanity from the frightful specter of nuclear weapons,” its ambassador, Nozipho Mxakato-Diseko, said. “For us, as a country, it was a duty to vote ‘yes’ for this treaty … to have voted ‘no’ would have been a slap in the face to the victims of Hiroshima and Nagasaki.”

One nation participating in ban negotations, the Netherlands—which hosts US nuclear weapons on its territory—did opt to vote against the treaty. Its government opposes meaningful disarmament efforts, despite overwhelming public support.

All nine nuclear-armed nations boycotted the negotiations, and therefore were absent for the vote. Some had exerted great pressure on other nations not to participate. But ultimately they failed to thwart the process. The commitment and resolve of the international community to declare nuclear weapons illegal was evident from the beginning of negotiations.

The treaty prohibits its state parties from developing, testing, producing, manufacturing, transferring, possessing, stockpiling, using, or threatening to use nuclear weapons. It also prohibits them from assisting, encouraging, or inducing anyone to engage in any of those activities, and they must not permit nuclear weapons to be stationed on their territory.

A nation that possesses nuclear weapons may join the treaty, so long as it agrees to remove them from operational status immediately and destroy them in accordance with a legally binding, time-bound plan. One that hosts another nation’s nuclear weapons on its territory may also join the treaty on condition that it will remove them by a specified deadline.

The treaty will open for signature in New York on September 20th, when world leaders meet for the annual opening of the UN General Assembly. “If you love this planet, you will sign this treaty,” said Setsuko Thurlow. Fifty nations will need to ratify it before it can enter into full legal force. Much work will then be needed to ensure that it is implemented and becomes universal.

With close to 15,000 nuclear weapons remaining in the world—and efforts underway in all nuclear-armed nations to bolster their arsenals—the ultimate goal of eliminating this paramount threat to humanity is far from being realized. But now, the United Nations has established the foundations for making a nuclear-weapon-free world possible.

The treaty establishes a powerful norm that, many expect, will prove transformative. It closes a major gap in international law. Nuclear weapons—like other indiscriminate weapons, including biological and chemical weapons, anti-personnel landmines and cluster munitions—are now categorically and permanently banned.

This post is part of Ban Brief, a series of updates on the historic 2017 negotiations to create a treaty banning nuclear weapons. Ban Brief is written by Tim Wright, Asia-Pacific director of the International Campaign to Abolish Nuclear Weapons, and Ray Acheson, director of Reaching Critical Will.