The Union Army, the Army of Northern Ireland and the Army National Liberation Front (ALF) are calling for an international military force to fight the Islamic State group.
The calls for a united army were made at a rally in London organised by the Stop the War Coalition (SWE), a UK-based organisation that is campaigning for a ceasefire between the US and Russia.
Organiser Mark Elliott said the call was a response to President Donald Trump’s declaration of a war against IS and the US withdrawal from Afghanistan.
“I think the world is now at a turning point and it is the most important time since the end of the Cold War,” he told Al Jazeera.
“We need a new international organisation and we need an army.”
Mr Elliott said it would be a “mistake” for the US to be leading an international force.
“If the United States is going to lead an international army, then they should have a plan for how to fight and where to fight it,” he said.
“That is what the international organisation is supposed to do, to organise international forces and then coordinate them.”
The call comes as the US military has been embroiled in a string of incidents involving American soldiers and civilians.
In July, an American soldier was killed by a roadside bomb in northern Afghanistan.
The US military is investigating the death of a British citizen who was shot by a US soldier while serving in Iraq.
The group said the decision to call for a UN force to combat the Islamic state was a result of the recent terrorist attacks in Paris and Brussels, which it said had been fuelled by IS sympathisers in Europe.SWE, which has organised similar calls, said that since its inception, it has helped hundreds of thousands of people in conflict-ridden regions of the world.
The organisation said its members, who include soldiers, police and firefighters, would support an international peacekeeping force to “stop the violence and terrorism that is destroying our communities, nations and world”.
“There is no way to stop this bloodshed.
Our country cannot survive the threat of IS, which is destroying every nation on earth,” it said in a statement.