When the president of the United States travels abroad, a mini White House travels with him. Part of the staff accompanying him stay on in Air Force One, his official aircraft, and part of them stay in the same hotel as he does.
Their job is to ensure his security, in coordination with the intelligence and security agencies of the host country, to keep him posted continuously with important developments all over the world and to enable him to remain in continuous contact with members of his Cabinet not traveling with him and the chiefs of his intelligence agencies and armed forces.
His visit to India and Pakistan is the second most dangerous trip President George W Bush would be undertaking since he took office in January 2001.
The first was his hit-and-run trip to Baghdad on Thanksgiving Day in November 2003, to visit some of the US troops which had participated in the invasion of Iraq.
He clandestinely took off for Baghdad from a military base in the US with a select group of journalists, who were sworn to secrecy and not told where he was going, flew directly to Baghdad, met some of the troops at the airport, took off and returned to the military base.
Only then did the public get to know about this visit. It was a very well-guarded secret and a well-carried out operation.
His visit to India and Pakistan -- and possibly Afghanistan too --- are to areas which continue to be badly affected by international jihadi and Maoist terrorism, both of which are strongly anti-US.
Al Qaeda, the Taliban and the various components of Osama bin Laden's International Islamic Front are operating from sanctuaries in the Waziristan area of Pakistan.
While the Al Qaeda itself has not been active in India so far, four Pakistani components of the IIF -- Lashkar-e-Tayiba, Harkat-ul-Mujahideen, the Harkat-ul-Jihad-al-Islami and Jaish-e-Mohammad -- are active in Jammu and Kashmir and other parts of India.
The Maoists have been active in Nepal and many states of India, including Andhra Pradesh which Bush intends to visit.
The risk to Bush would be graded as extremely high if he decides to go to Afghanistan, very high in Pakistan and high in India.
Since his visit to this region is open and not a secret as it was to Baghdad, providing him with effective physical security would call for the best in human and technical resources the intelligence and security agencies of the US, India, Pakistan and Afghanistan are capable of, and would involve effective coordination among them.
Among the physical security threats one would be concerned with are those which could arise from heat-seeking surface-to-air missiles, improvised explosive devices activated mechanically or through chemical timers or through remote-controlled devices and suicide bombers.
Time-tested methods such as evasive techniques to escape heat-seeking missiles, jammers to neutralise remote-controlled IEDs, strict access control to prevent any attempt at suicide terrorism, anti-explosive and anti-firearm checks etc would be used by all agencies concerned to ensure effective security.
While the visit itself is open, the sensitive details of the visit such as his mode of transport inside the cities to be visited by him, the routes to be taken etc will be kept a closely guarded secret till the last minute.
Among the evasive techniques often employed are arriving before or after the publicly-announced time of arrival, changing the aircraft etc.
When former president Bill Clinton visited Pakistan from India in 2000, the visit was kept a closely-guarded secret.
He did not fly directly to Islamabad from India. He flew in Air Force One from India to Qatar, left his plane there, got into a smaller aircraft of the US Air Force and flew to Islamabad.
He returned to Qatar by the same aircraft, got into Air Force One and flew back to Washington, DC.
Before he went to Islamabad from Qatar, another aircraft of the same type, carrying a double of Clinton from the Central Intelligence Agency, landed in Islamabad.
Clinton's double was received by the Pakistani officials and taken to the office of General Pervez Musharraf.
An announcement was made that Clinton had arrived. Subsequently, the real Clinton arrived in a similar plane.
Such evasive techniques may not be necessary for India. It remains to be seen whether the US Secret Service, which is responsible for Bush's protection, would advise him to adopt evasive techniques in Pakistan.
Evasive techniques may also be required against heat-seeking missiles. Among the techniques generally followed are to fire a number of flares when the VIP aircraft is about to take off or land which will mislead the heat-seeking mechanism of the missile, or for the pilot to skilfully dodge the missile.
The Russians used to fire flares in Afghanistan to escape the Stinger missiles fired by the mujahideen.
When terrorists suspected to be from the Al Qaeda fired a heat-seeking missile at an Israeli commercial plane taking off from Mombasa in October 2002, the pilot noticed it from the air and dodged it.
Similarly, in November 2005, a US Air Force helicopter pilot deputed to Pakistan-Occupied Kashmir for quake relief managed to dodge a suspected missile from the ground.
The danger from heat-seeking missiles is that one can evade them only if one sees them being fired or approaching the aircraft.
Normally, as a security precaution, an hour or so before the arrival of the plane, the security agencies and the air force of the host country and the visiting dignitary's country make a ground and helicopter search to make sure that nobody with a shoulder-fired missile has taken up position near the airport.
Collection of preventive intelligence is an important component of effective physical security. Human sources at the disposal of the intelligence agencies of the four countries would have already been tasked with looking around for any suspicious activity or indicator, which could have a bearing on the president's security.
Similarly, the National Security Agency, which is the principal technical intelligence agency in the US, and the techint agencies of India, Pakistan and Afghanistan would already be closely monitoring all electronic communication of a suspicious nature originating from or passing to this region -- over telephone and wireless as well as through the Internet.
While the physical security staff accompanying the president would focus their entire attention on protecting him, special communications staff from the NSA and other sensitive agencies accompanying the president will perform the task of enabling him to continue to function effectively as the president of the US and the commander-in-chief of its armed forces wherever he may be.
They will set up special communication rooms in the presidential aircraft wherever it is parked, in his place of stay and in the US embassy.
There will be a continuous flow of thousands of coded messages between the president's place of stay and Washington, DC.
The NSA staff accompanying him with their equipment will ensure that the president is able to talk to anybody anywhere in the world wherever he may be.
So far as functioning as the president of the US is concerned, Bush will find no difference between functioning from the White House and from the place of stay in the country being visited by him.
He would have at his disposal secure communication facilities of very high quality.
In Washington, DC, the president starts his day by going through the Daily Intelligence Summary prepared by the CIA director on important developments all over the world the previous day.
If necessary, the CIA director also meets the president for a personal briefing.
When the president travels abroad, a team of senior CIA officers travels with him.
Every morning the CIA director sends to the leader of this team his DIS. This officer puts it up to the travelling president and answers his questions.
When the president is in India, the techint agencies of India and the intelligence officers of other countries posted in their embassies in India will try to intercept all communication passing between Washington, DC, and the president's camp in India.
This could help them understand the pattern of American communication and their coding and decoding systems.