The American 101st Airborne Division encircled the Shiite holy city of Najaf on Sunday, seizing a critical airfield and preparing for a possible incursion into the city to hunt for guerrilla fighters who have already attacked supply convoys and at least one military checkpoint.

Coalition forces have not said whether the move is to simply cordon off the city of 300,000 as forces continue north toward Baghdad or whether troops will attempt to take the city.

If troops do attempt to take the city, U.S. military planners face not only the challenges posed by urban combat, but the prospect of doing battle in one of Islam's holiest cities.

A holy city for Muslim's Shiites

Najaf is the resting place of Imam Ali Ibn Abu Talib, the Prophet Muhammad's cousin and son-in-law and Shiites' most revered saint.

Ali's shrine, in the heart of the city, is considered by many as one of the landmarks of Islamic art, with its silver-covered tomb, highly ornamented walls and golden dome.

The city itself is also the seat of Shiites' spiritual leaders, or ayatollahs, and the center for academic and theological studies for the Islamic world. For the Shiites, it is the third most holy city in Islam after Mecca and Medina in Saudi Arabia.

The city is so revered that it overlooks the world's largest cemetery, where Shiites hope to be buried.

Najaf's military importance

But the city, one of the critical junctions in the U.S.-led march north towards Baghdad, has also been the scene of deadly and intense fighting. North of the city, a U.S. military checkpoint was attacked by a suicide bomber Saturday, killing four soldiers.

Najaf also could serve as a base for militants loyal to Saddam Hussein to attack coalition supply lines, as has been the case in Nasiriya to the south.

Officers with the 101st Airborne said all efforts were being made to make sure holy sites would not be damaged, except in self defense.

"We take our responsibility to these things very seriously and treat them with the utmost respect," Capt. Micah Pharris, an attorney in the 101st Airborne's judge advocate general's office, told the Associated Press.

Impact of a possible attack

Shiite clerics have also warned that any perceived attack on the holy sites in Najaf would provoke severe reactions.

"I don't think that anyone dares to attack a holy site in Iraq. An attack on holy shrines will only provoke the uncontrolled anger of Muslims, especially Shiites, with serious consequences to the attackers," Ibrahim Khalili, a prominent Iranian Shiite clergyman, said.

For now, the 101st has encircled the city and awaits further orders from U.S. Central Command. But senior military officials have told reporters that there are too many militants inside Najaf to ignore the city in the push north -- planners must either leave troops around the city or move door-to-door to root out pro-Saddam militia members.

Shiite - (n.) a Muslim of the Shia branch of Islam

incursion - (n.) a hostile entrance into a territory (Merriam-Webster)

guerrilla - (n.) member of an irregular military force fighting small-scale, limited actions against conventional military forces. Guerrilla tactics involve constantly shifting attack operations and include the use of sabotage and terrorism. (Encyclopedia Britannica)

cordon off - (transitive v.) to form a protective or restrictive cordon around (Merriam-Webster)

cordon - (n.) a line of troops or of military posts enclosing an area to prevent passage (Merriam-Webster)

Associated Press - (n.) an organization that provides news to newspapers, television, radio and other media outlets

U.S. Central Command - (n.) Headquartered at MacDill Air Force Base in Tampa, Florida, United States Central Command (USCENTCOM) is one of nine Unified Combatant Commands assigned operational control of U.S. combat forces. A Unified Combatant Command is composed of forces from two or more services, has a broad and continuing mission, and is normally organized on a geographical basis into regions known as "Areas Of Responsibility" (AORs). USCENTCOM’s AOR stretches from the Horn of Africa to Central Asia. (www.centcom.mil)