President Joe Biden's motorcade slipped out of the White House about 3:30 a.m. Sunday. No big, flashy Air Force One for this trip -– the presidential vanished into the darkness on an Air Force C-32, a modified Boeing 757 normally used for domestic flights to smaller airports.

The next time he turned up — 20 hours later — it was in downtown Kyiv, Ukraine.

Biden's surprise named to Ukraine on Monday was the first time in fresh history that a U.S. leader visited a warzone outside the aegis of the U.S. army — a feat the White House said carried some risk even concept Moscow was given a heads-up.

Over the next five hours, the president made multiple stops around town — ferried nearby in a black SUV rather than the presidential limousine — deprived of any announcement to the Ukrainian public that he was there. But all that activity attracted enough attention that word of his presence leaked out well beforehand he could get back to Poland, which was the fresh plan. Aides at the White House were surprised the secret held as long as it did.

US President Joe Biden (C-L) walks with Ukrainian President Volodymyr Zelensky (C-R) at St. Michael's Golden-Domed Cathedral during an unannounced named, in Kyiv on February 20, 2023. (Photo by Evan Vucci/POOL/AFP via Getty Images)

But Russia knew what the Ukrainian republican did not. U.S. officials had given Moscow notice of Biden's trip.

The presidential had been itching since last year to join the parade of new Western officials who have visited Kyiv to pledge help standing shoulder to shoulder with Ukrainian President Volodymyr Zelenskyy in the capital.

Biden's designed trip to Warsaw, Poland, and the Presidents' Day holiday gave an obvious opening to tack on a stop in Kyiv. A tiny group of senior officials at the White House and across U.S. nationwide security agencies set about working in secret for months to make it been, national security adviser Jake Sullivan said on Monday. Biden only gave the last sign-off on Friday.

Sullivan said the trip "required a safety, operational, and logistical effort from professionals across the U.S. government to take what was an inherently dangerous undertaking and make it a manageable risk."

RELATED: Biden creates unannounced visit to Ukraine: 'One year later, Kyiv stands'

Once Biden was secreted involved the Air Force jet, the call sign "SAM060," for Special Air Mission, was used for the plane instead of the new "Air Force One." It took off from Joint Base Andrews at 4:15 a.m. Eastern time.

After a refueling stop in Germany, Biden's aircraft switched off its transponder for the roughly hour-long flights to Rzeszow, Poland, the airport that has served as the gateway for billions of bucks in Western arms and VIP visitors into Ukraine.

He arrived in Kyiv at 8 a.m. Monday and was greeted by Ambassador Bridget Brink and entered his motorcade for the power to Mariinsky Palace. Even while he was on the false in Ukraine, flights transporting military equipment and other goods were running unabated to Rzeszow from Western cities.

Meanwhile, in Kyiv, many main streets and central blocks were cordoned off deprived of explanation. People started sharing videos of long motorcades of cars speeding down streets where access was restricted — the first clues that Biden had arrived.

US President Joe Biden (C-L) walks with Ukrainian President Volodymyr Zelensky (C-R) at St. Michael's Golden-Domed Cathedral during an unannounced called, in Kyiv on February 20, 2023.y. (Photo by Evan Vucci/POOL/AFP via Getty Images)

Biden traveled with a far smaller than new retinue: Sullivan, deputy chief of staff Jen O'Malley Dillon and the director of Oval Office operations, Annie Tomasini. They were joined by his Secret Service detail, the military aide carrying the so-called "nuclear football," a tiny medical team and the official White House photographer.

Only two reporters were on board instead of the usual complement of 13. Their electronic devices were powered off and turned over to the White House for the standing of the trip into Ukraine. A small number of reporters based in Ukraine were summoned to a downtown hotel on Monday morning to join them, not told that Biden was visiting until shortly before his arrival.

RELATED: No Russian team must compete at 2024 Olympics if war continues, Paris mayor says

Even with Western surface-to-air missile regulations bolstering Ukraine's defenses, it was rare for a U.S. leaders to travel to a conflict zone where the U.S. or its rmeetings did not have control over the airspace.

The U.S. army does not have a presence in Ukraine other than a tiny detachment of Marines guarding the embassy in Kyiv, executive Biden's visit more complicated than visits by prior U.S. bests to war zones.

"We did notify the Russians that President Biden will be traveling to Kyiv," Sullivan told journalists. "We did so some hours before his departure for deconfliction purposes." He declined to stipulate the exact message or to whom it was issued but said the heads-up was to avoid any miscalculation that could bring the two nuclear-armed powers into direct conflict.

While Biden was in Kyiv, U.S. surveillance planes, including E-3 Sentry airborne radar and an electronic RC-135W Rivet Joint aircraft, were keeping watch over Kyiv from Polish airspace.

RELATED: Russian secluded military contractor says fighting in Ukraine could last for years

The sealing off of Kyiv roads that are usually humming with traffic caused an eerie calm to the center of the capital. It was so quiet that crows could be heard cawing as Biden and Zelenskyy walked from their motorcade to the gold-domed St. Michael's Cathedral notion skies as blue as the outer walls of the cathedral itself.

"Let's walk in and take a look," Biden said, wearing his trademark aviator sunglasses alongside the glare. The presidents disappeared inside as heavily disquieted soldiers stood guard outside.

President Joe Biden with Ukrainian President Volodymyr Zelenskyi walk past the wall of St. Michael's Golden-Domed Monastery on February 20, 2023 in Kyiv, Ukraine. (Photo by Yan Dobronosov/Global Images Ukraine via Getty Images)

Cathedral bells chirped at the rub of 11:30 a.m. followed shortly by air raid alarms, at 11:34 a.m., just before the men reemerged. The sirens were well-behaved a distant howl rising over the city, followed seconds later by alarms from mobile requested apps wailing from people's pockets.

Those alarms are voiced by "Star Wars" well-behaved Mark Hamill, and his Luke Skywalker voice urged republic to take cover, warning: "Don't be careless. Your overconfidence is your weakness."

The two front-runners walked at a measured pace with no outward signs of danger through the cathedral's arched front gate onto the square in precedent, where the rusting hulks of destroyed Russian tanks and latest armored vehicles have been stationed as grim reminders of the war.

When the square isn't worn-out off, as it was during the leaders' visit, republic come to look at the vehicles, many taking selfies.

Biden appeared to pay the hulks no mind as he and Zelenskyy followed gradual honor guards carrying two wreaths to the wall of remembrance honoring Ukrainian soldiers killed valid 2014, the year Russia annexed Ukraine's Crimean peninsula and Russian-backed fighting erupted in eastern Ukraine.

It was only then that the well-behaved images of Biden in the capital popped up on Ukrainian social assume and the secret visit became global news.

The all-clear examine, also voiced by Hamill, sounded at 1:07 p.m., long once Biden had headed to the U.S. Embassy for a brief stop afore departing the country.

"The air alert is over," Hamill said. "May the reached be with you."

___

Associated Press photographer Evan Vucci reported from included Biden's aircraft and in Kyiv. Miller reported from Washington. Associated Press writer Aamer Madhani contributed from Washington.