Many among the group of about 60 veterans and family members were clad in military fatigues as they assembled in the rotunda of the Cannon House Office Building, unfurling banners that read “End the War on Iran” and “We Can’t Afford Another War” as they stood stoically at attention.

The veterans held a flag-folding ceremony to symbolise American service members who have died in the war and who might be killed if it resumes. Several were seen holding red tulip flowers in honour of Iranians killed during the war that US president Donald Trump and Israeli Prime Minister Benjamin Netanyahu began on Feb 28.

“This war is already deeply unpopular, and it is already a crisis for the Trump administration,” Mike Prysner, executive director of the Center on Conscience and War (CCW), said in a statement before he was arrested.

“More than 100 service members have already started to file as conscientious objectors. But if even more stand up, and some speak out, we have a real chance of deepening this crisis for Trump in a way that forces them to pull back from this war,” he added.

Prysner was using an acronym to refer to conscientious objectors, or service members who refuse to engage in a war they believe is immoral.

Roughly five dozen protesters were arrested by US Capitol Police for their act of civil disobedience, according to the centre.

“My advice to troops still serving is this: This is the most important historical moment of our lifetime, and what you choose to do matters. I can tell you from experience that continuing to help the war machine will only cause you more pain,” said Tyler Romero, a client of the CCW.

The protest was organised by a coalition of organisations, including About Face, Veterans For Peace, Common Defence, CCW, the Fayetteville Resistance Coalition, Military Families Speak Out and 50501 Veterans.