Israel says it has carried out an evacuation of members of Syria's White Helmets civil defence group from a war zone in south-western Syria.
Some 422 volunteers and family members were taken to Jordan via the Israeli-occupied Golan Heights overnight.
The UK, one of the nations requesting Israel's help, hailed the operation and will assist with resettlement.
The White Helmets describe themselves as a volunteer workforce that acts to save people in Syria's war zones.
Supporters of Syrian President Bashar al-Assad, and his Russian allies, say the White Helmets support the rebels and also have links to jihadist groups.
How did the operation come about?
The Israel Defense Forces (IDF) said they were acting on a request from the US, the UK and other European nations.
The White Helmets had become trapped in an area of south-western Syria near the border with the Golan Heights after an offensive by the Syrian military.
The offensive, begun in June, has seen a number of agreements that have led to the evacuation of rebel forces from the Deraa and Quneitra areas to regions further north.
The White Helmets operate only in rebel-held areas, although they say they are non-partisan.
How was it carried out?
The evacuees were driven to the border with the Golan Heights and taken on from there by Israeli troops to Jordan.
The plan had been to evacuate 800 White Helmets and their families, but only 422 made it.
The BBC's Mark Lowen says the others have been hemmed in by the expansion of Islamic State group fighters into pockets of south-west Syria and, as this was a one-off operation, fears remain for the fate of those left behind.
Those successfully evacuated included about 100 White Helmets, with the rest family members.
What have Israel and Jordan said?
The IDF said they had "completed a humanitarian effort to rescue members of a Syrian civil organisation and their families", saying there was an "immediate threat to their lives".
The civilians were evacuated from the war zone in Southern Syria due to an immediate threat to their lives. The transfer of the displaced Syrians through Israel is an exceptional humanitarian gesture— IDF (@IDFSpokesperson) July 22, 2018
Although Israel is not directly involved in the Syria conflict, the two countries have been in a state of war for decades.
Despite the intervention, the IDF said that "Israel continues to maintain a non-intervention policy regarding the Syrian conflict".
Jordan's government confirmed it had "authorised the United Nations to organise the passage of 800 Syrian citizens through Jordan to be resettled in Western countries".
What happens next?
The White Helmet volunteers and their families will be held in a "restricted area" of Jordan and assessed by the UN, pending resettlement.
Jordan said that "Britain, Germany and Canada made a legally binding undertaking to resettle them within a specified period of time due to 'a risk to their lives'."
The UK confirmed it would help with the resettlement, providing protection to "as many of the volunteers and their families as possible".
A statement from Foreign Secretary Jeremy Hunt and International Development Secretary Penny Mordaunt said: "White Helmets have been the target of attacks and, due to their high profile, we judged that, in these particular circumstances, the volunteers required immediate protection.
"We pay tribute to the brave and selfless work that White Helmet volunteers have done to save Syrians on all sides of the conflict."
Fantastic news that we - UK and friends - have secured evacuation of White Helmets and their families - thank you Israel and Jordan for acting so quickly on our request. The WH are the bravest of the brave and in a desperate situation this is at least one ray of hope— Jeremy Hunt (@Jeremy_Hunt) July 22, 2018
Who are the White Helmets?
Their official name is the Syrian Civil Defence and it began in early 2013 as an organisation of volunteers from all walks of life, including electricians and builders.
Its main task soon became to rescue civilians in war zones in the immediate aftermath of air strikes, and it says its volunteers have saved the lives of more than 100,000 people during the civil war.
Numbering about 3,000 volunteers, they also carry out essential repair works. Some 200 members have been killed.
The White Helmets have gained worldwide praise, were nominated for the 2016 Nobel Peace Prize and were the subject of a Netflix documentary and BBC Panorama programme.
But Syria's government and its ally Russia have accused the group of links to jihadist groups.
President Assad said it used "humanitarian masks and umbrellas just to implement a certain agenda".
The group has been financed by public donations, as well as funding from foreign governments.