The grand military parade that United States President Donald Trump had been wanting for years barrelled down Washington, DC’s Constitution Avenue, with tanks, troops and a 21-gun salute, the spectacle played out against a counterpoint of protests around the country by those who decried the Republican leader as a “dictator” and “would-be king”.

Trump, also celebrating his 79th birthday, sat on a special viewing stand south of the White House to watch the display of US military might, which began early on Saturday and moved swiftly as light rain fell and clouds shrouded the Washington Monument.

The procession, with more than 6,000 soldiers and 128 tanks, was one Trump tried to hold in his first term after seeing such an event in Paris in 2017, but the plan never came together until the parade was added to an event recognising the US Army’s 250th anniversary.

As armoured vehicles rolled down the street in front of the president, millions of people packed into streets, parks and plazas across the US as part of the so-called “No Kings” protests, marching through city centres and small towns, blaring anti-authoritarian chants mixed with support for protecting democracy and immigrant rights.

Authorities across the US urged calm and promised no tolerance for violence, while some governors mobilised the National Guard ahead of the demonstrations.

Police in Los Angeles, where protests over federal immigration enforcement raids erupted a week ago, used tear gas and crowd-control munitions to clear out protesters after the formal event ended. Officers in Portland city also fired tear gas and projectiles to disperse a crowd that protested in front of a US Immigration and Customs Enforcement (ICE) building well into Saturday evening.

Huge, boisterous crowds marched, danced, drummed and chanted shoulder-to-shoulder in New York City, Denver, Chicago, Austin and Los Angeles, some behind “No Kings” banners. Atlanta’s 5,000-capacity event quickly reached its limit, with thousands more gathered outside barriers to hear speakers in front of the state Capitol. Officials in Seattle estimated that more than 70,000 people attended the city’s largest rally in the city centre, the Seattle Times reported.

The demonstrations came on the heels of protests over the federal ICE raids which began last week, and Trump’s order for the US National Guard and Marines to be deployed to Los Angeles, where protesters blocked a motorway and set cars on fire.

“Today, across red states and blue, rural towns and major cities, Americans stood in peaceful unity and made it clear: we don’t do kings,” the No Kings Coalition said in a statement on Saturday.