It wasn’t that many years ago – 2008, in fact – that Nelson Mandela’s name was still on the US terrorist watch list (officially, anyway) for having been a leader of the African National Congress, which advocated armed resistance to South Africa’s white minority regime.

That’s when US officials embarrassedly removed his name from the list, by which time Mr. Mandela already was seen as a hero for having peacefully led South Africa out of apartheid, becoming the country’s first freely elected president, winning a US Presidential Medal of Freedom and a Nobel Peace Prize.

Today, flags around the US are being flown at half-staff in honor of Mandela, a rare honor for a foreign leader that puts him in company with Winston Churchill and Pope John Paul II.

This week, President Obama – together with former presidents George W. Bush, Bill Clinton, and Jimmy Carter – will travel to Johannesburg along with some 50 other heads of state to attend the memorial service for Mandela.

The “ceremony of remembrance” Tuesday will be held in the Soweto soccer stadium, which holds 94,000 people.

A large, open venue like that would present a massive security challenge under any circumstances. But with just a few days' notice since Mandela’s passing three days ago, it’s meant unusual scrambling for the Secret Service and other agencies.

Dozens of agents, armored presidential vehicles, travel and logistics officials are on their way. Some from US diplomatic and military sites in Africa and Europe are already there.

“It’s an event that’s being planned by the host government,” Dan Rosenthal, who was responsible for planning public events around the world for former president Clinton, told Politico.com. “In terms of the logistical challenges, they’re immense in terms of the compressed timeline, months now into days.”

“They try to make the best of the situation,” Mr. Rosenthal said. “They try to get their guys as close as possible and get guys pre-positioned along the route to have as much situational awareness as they can. They don’t have the same level of control as they normally do.”

When the president appears at an American stadium, officials bring metal detectors and screeners at the entrances, Politico reports. In Johannesburg, the Secret Service won’t have that sort of control of the situation – which means that Mr. Obama and other dignitaries will almost certainly be positioned behind bulletproof glass or in a protected box.

The potential for confusion and complication is multiplied by the number of other countries’ leaders who will be attending the memorial service, bringing their own security apparatus with them.

That includes Britain’s Prince Charles and Prime Minister David Cameron, French President Francois Hollande, UN Secretary General Ban Ki-moon, and at least two dozen members of the US Congress.

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Without detailing specifics, those charged with providing security for the president and other US officials say they’ll be ready on Tuesday.

“We’re used to working on short notice,” Secret Service spokesman Ed Donovan told Politico. “The president and vice president often go places on short notice. Things like this like funerals, nationally significant events they go to with just a day or two notice.”