When the president went to Baghdad on Thanksgiving in 2003, it was a top-secret operation not made public until he had left Iraq.
Today, he flew into Pakistan on a trip that has been public for two weeks now, a trip that will present perhaps the greatest physical risk to him since he took office.
"I'm sure when President Bush arrives there, there will be very special extra security measures because if any place is going to have an attack on the president, it is going to be Pakistan," Richard Clarke, a former counterterrorism official and now an ABC News consultant, said before the trip.
Pakistan's major cities are places where al Qaeda and other militant Islamist groups thrive. In fact, in the last year, new al Qaeda training camps have actually opened inside Pakistan.
In those camps, Osama bin Laden is hailed as a hero, and the Pakistani and American presidents are seen as infidels.
Pakistan is "a country with thousands, if not tens of thousands, of militants who have been subcontracted by al Qaeda, and some of whom rub shoulders with senior members of the military," said Alexis Debat, an ABC News consultant and a senior fellow at George Washington University's Homeland Security Policy Institute.
'Most Serious Concern'
Bush was scheduled to spend 24 hours in the capital, Islamabad, where there have been, in the last few years, at least three known attempts on the life of Pakistani President Pervez Musharraf.
Debat pointed out that one of the attempts involved placing explosives in a tunnel under the runway where Bush is slated to land.
When President Clinton went to Pakistan in March 2000, the Secret Service used elaborate deceits to throw potential assassins off the trail.
Jennifer Palmieri, Clinton's former deputy press secretary, said she and her colleagues at the time knew it was "a very risky proposition [and] the Secret Service was not happy."
"They don't ever quite recommend against trips, they do, this was the most serious concern I think that they ever expressed about a trip that we did end up taking," she said.
On that trip, Air Force One flew in without the president.
"The plane door opened, and a Secret Service agent resembling Bill Clinton walked off the plane," Palmieri said.
The president was actually flown in on a small, executive jet. "It was the only time that I traveled with Clinton where I was actually scared," she added.
There were two motorcades from the airport. One was a decoy.
"The real threat in Pakistan is that someone on the inside, someone in the Pakistani military or intelligence service, might be cooperating with the terrorists," Clarke said. "It has happened many times in Pakistan, and it is very hard to protect against an inside threat."
Message From the Militants?
The suicide bomb attack Thursday outside the U.S. consulate in Karachi has only added to concerns for the president's safety.
The force of the blast was a powerful message -- the aftermath, a jumble of burning cars scattered between the U.S. consulate and a Marriott hotel.
At least four people, including a U.S. diplomat, were killed and more than a dozen injured.
According to a security video described to ABC News, a U.S. consulate Toyota Land Cruiser, carrying an American diplomat, approached the back street to the consulate at 8:58 a.m.
Parked on the street in a spot reserved for Pakistani naval officers, the suicide bomber waited 18 minutes and then backed into the Land Cruiser.
The blast was so powerful that it blew the fully armored U.S. car, weighing more than 3 tons, 40 feet into the air into the parking lot of the Marriott hotel.
"The explosion caused this 6-foot crater in the cement," said Gretchen Peters, an ABC News producer who was on the scene. "This was a massively powerful explosion, and the results are grisly."
Weighing the Possibility of an Attack
The State Department identified the dead American as David Foy, 52, of North Carolina. He had worked there since September.
In India on Thursday, Bush said the attack would not stop from him visiting Pakistan.
"The bombing that took place prior to my trip is an indication that the war on terror goes on and that free nations must come together to fight terrorism," he said.
Clarke said, "Al Qaeda normally avoids high secure targets such as Olympics and other events like that because the security is so high."
But, he added, "there are so many groups in Pakistan that have an interest in embarrassing President Musharraf and President Bush that the probability of one of them trying something while the president is there is very high."