CRAWFORD, Texas Running for president, George W. Bush could not name the new leader of Pakistan. But after the Sept. 11 attacks, Pervez Musharraf became a crucial but ultimately frustrating ally in the war against extremists.

The embattled Musharraf, who resigned on Monday, angered many Pakistanis by siding with the United States. He disappointed Washington by failing to be tougher with al-Qaida and the Taliban in Pakistans lawless northwest border region. He pledged support for democratic reforms in Pakistan, yet it was Musharrafs dictator-like actions that eventually unraveled his nearly decade-long rule.

Bush came to call him the indispensable man, Bruce Riedel, a senior adviser to three presidents on Middle East and South Asian affairs told Reuters. In the end, he also became the man who couldnt deliver. Bush was very slow to realize that he either had been had by Musharraf or that Musharraf was not up to the task. Historians will debate this for years.

Musharraf was Washingtons key ally in the fight against insurgents on the Afghan-Pakistan border, although the strength of the insurgents on both sides of the border increased substantially during his term as army chief. An agreement he signed with insurgents in 2006 is often cited as having given room to al-Qaida to regroup in Pakistans South Waziristan tribal region.

His resignation pressures Pakistans newly elected government to provide new leadership in the countrys fight against militants. The Bush administration is in regular contact with the new government, and the president is expected to have phone conversations in the near future with high-level Pakistani officials, White House deputy press secretary Gordon Johndroe told reporters Tuesday. He spoke in Crawford, Texas, where Bush is vacationing at his ranch.

In November 1999, when Bush was running for the White House, Bush new little about Musharraf, the general who had seized power in a military coup the previous month. When a TV reporter asked him to name the new Pakistani leader, Bush replied The new Pakistani general, hes just been elected _ not elected, this guy took over office.

But Bush could not remember his name. General. I can name the general. General, he said, a bit irritated by the pop quiz on foreign policy.

A month after the Sept. 11, 2001, terrorist attacks, Musharraf was standing with the now-President Bush at the Waldorf Astoria in New York, declaring Pakistans unwavering support to fight with the United States against terrorism in all its forms wherever it exists.

Bush and Musharraf got along from the start. They both saw themselves as straight-shooters who did not wring their hands over decision-making. Bush and Musharraf, who has had plenty of knowledge about the United States, his brother is a doctor in Chicago, struck up a workable friendship. Musharraf is known to enjoy dancing to Western music at parties.

Despite their rapport, theirs was an alliance of convenience.

Bush needed help catching terrorists, and he wooed Musharraf because the general had a reputation as someone who would bring stability to Pakistan. Musharraf curried Bushs favor to earn support from the ruling class in Pakistan that believed their nations path was determined by Allah, the Army, and America, as Pakistans ambassador to the United States, Husain Haqqani, put it.

It wasnt a personal relationship, but Musharraf tried to play it, effectively, for domestic advantage, he said.

Over time, Bush and Musharraf each suffered politically from their friendship. Bush was accused of looking the other way when Musharraf did not play by the rules of democratic nations. The Pakistani leaders alliance earned him the unfriendly nickname of Mush, which rhymes with Bush.

Some Pakistanis claim it was Musharrafs relationship with Washington that was to blame for many of the countrys problems, including the rising tide of extremist attacks within Pakistan.

We pretty much played the Musharraf card, ad nauseam, eventually to Pakistans detriment, said Rick Barton, a Pakistan expert at the Center for Strategic and International Studies.

Late last year, Bushs confidence in Musharraf, however, began to crack. In November 2007, Musharraf declared a state of emergency in Pakistan, suspended the constitution and dismissed independent-minded judges as the Supreme Court was set to rule on the legality of his October 2007 election, a ballot that was boycotted by the opposition.

Bush said it would be hard for him to argue that Musharraf was still trying to advance democracy if he did not lift emergency rule before upcoming parliamentary elections.

So far, Ive found him, Bush said.