Thousands of soldiers, tanks and aircraft will be on show in Washington as the United States Army marks its 250th birthday on Saturday local time, culminating in a massive military parade.
The last time the US held such an event was in 1991 under president George HW Bush to mark the end of the Gulf War.
The event — which coincides with US President Donald Trump's 79th birthday — will likely divide the American public, Todd Belt of George Washington University said.
"If you like Donald Trump you're going to love this," Professor Belt said.
"You're going to this as he is being strong and making America great again and restoring America's greatness. If you hate him, you're going to see this as a vast expenditure and a pseudo-fascist sort of exercise."
While the army has said it has no plans to recognise Trump's birthday, the president is expected to play a major role in the celebrations, which have been altered to include a parade the president has promised will be "like no other".
Professor Belt said staging a military parade in the US ran contrary to the country's political ethos.
"One of the things about authoritarian regimes and the use of military parades is that it creates a unity around the state and around the leader," he said.
"Whereas in the United States we came out of a revolution where we reject kings, and we are very individual here and so it's very different in the United States."
The displays and celebrations are set to cost the US Army between $US25 million ($38 million) and $US45 million, with some critics calling it an authoritarian display of power.
What we know about the military parade
The event is set to feature 6,600 soldiers, 150 vehicles, 50 aircraft and fireworks.
The celebration for the anniversary includes an army birthday festival on the National Mall before a parade through the capital and an enlistment and re-enlistment ceremony presided over by the president.
After the parade, the army's parachute exhibition team known as the Golden Knights will parachute in and present Trump with a flag.
While big military displays at this level are not as common in the United States, they are held regularly in countries such as North Korea and Russia who use them to try to intimidate or send a message to less friendly nations, and also to showcase their military might.
Pyongyang and Moscow also use such parades to celebrate their leaders, mark war anniversaries, as well as showcase their latest achievements in nuclear weapon advances.
The US Army displayed a range of military aircraft at Joint Base Andrews on Thursday as a preview of the upcoming celebrations.
Featuring CH-47 Chinooks, UH-60 Black Hawks, and AH-64 Apaches, the display showcased the Army's aviation capabilities and are part of a larger array of military equipment set to be featured in a flyover during Saturday's event.
What about protests on the weekend?
Several activist groups are planning more than 1,800 anti-Trump demonstrations across the country on the same day.
Organised by a group called No Kings, it follows several days of protests against federal immigration raids including in Los Angeles.
"They've defied our courts, deported Americans, disappeared people off the streets, attacked our civil rights and slashed our services," the group says on its website.
"The corruption has gone too far. No thrones. No crowns. No kings."
The president has promised protesters who do attend the Washington celebration that they will be "met with very big force".
Experts question timing
Australian Strategic Policy Institute senior analyst Malcolm Davis questioned the cost and timing of the parade given the demonstrations that were expected to take place across the country as well as in Los Angeles.
"It will be interesting to see how it goes, especially with the anti-ICE protests occurring across America — now taking the form of No Kings marches," Dr Davis told the ABC.
"To my knowledge, there aren't any demos planned for DC, but if one did, that could see a harsh response."
Davis said the parade seemed to be about one thing only — and it wasn't the US Army.
"I think Trump is trying to play to his base and also inflate his own ego and make himself the centre of attention," he said.
"He's also infatuated with authoritarian leaders like Putin and Kim Jong Un and their approach to power. So this parade is a gift to his own ego, at the expense of the US taxpayer."
with Reuters
