A week of terror strikes across Pakistan, capped by a stunning assault on army headquarters, show the Taliban have rebounded and appear determined to shake the nation's resolve as the military plans for an offensive against the group's stronghold on the Afghan border.

The 22-hour raid on Pakistan's "Pentagon" in the city of Rawalpindi, which ended with 20 dead Sunday, was the third terror attack in a week to shake this nuclear-armed nation. It demonstrated the militants' renewed strength since their leader was killed by a U.S. missile strike in August and military operations against their bases.

The attack followed warnings from police as early as July that militants from western border areas were joining those in the central Punjab province in plans for a bold attack on army headquarters. The suspected ringleader in Saturday's raid, known as Aqeel, also was believed to have orchestrated an ambush on Sri Lanka's visiting cricket team in Lahore this year.

The U.S. has long pushed Islamabad to take more action against Taliban and Al Qaeda militants, who are also blamed for attacks on U.S. and NATO troops in Afghanistan, and the army carried out a successful campaign against the militants in the Swat Valley in the spring.

SLIDESHOW: Pakistan Attacks

But the army had been unwilling to go all out in the lawless tribal areas along the border that serve as the Taliban's main refuge. Three offensives into South Waziristan since 2001 ended in failure and the government signed peace deals with the militants.

On the heels of the Swat victory, the military launched a campaign of airstrikes on the militants in Waziristan and in recent weeks officials said they were preparing a full offensive there.

That was before the embarrassing attack on army headquarters bolstered militants' assertions they are ready to take on the military, and threatened to deflate the army's newfound popularity.

In the wake of the seige in Rawalpindi, the government said it would not be deterred. The military launched two airstrikes Sunday evening on suspected militant targets in South Waziristan, killing at least five insurgents and ending a five-day lull in attacks there, intelligence officials said.

"We are going to attack the terrorists, the miscreants over there who are disturbing the state and damaging the peace," Information Minister Qamar Zaman Kaira said. "Wherever they will be, we will follow them. We will pursue them. We will take them to task."

In London, U.S. Secretary of State Hillary Rodham Clinton said the insurgents are "increasingly threatening the authority of the state, but we see no evidence they are going to take over the state." She and British Foreign Minister David Miliband said there was no sign Pakistan's nuclear arsenal was at risk.

Available information suggests that Pakistan's secret nuclear sites are protected by crack troops and multiple physical barriers.

"It's not thought likely that the Taliban are suddenly going to storm in and gain control of the nuclear facilities," said Gareth Price, head of the Asia program at London think tank Chatham House.

Security at army headquarters did not prevent a team of 10 gunmen in fatigues from launching a frontal assault on the very core of the country's most powerful institution Saturday morning, setting off a gunbattle and hostage drama that ended a day later after a commando raid.

The violence killed 20, including three hostages and nine militants, while 42 hostages were freed, the military said. Many of them had been held in a single room by a militant wearing a suicide vest, who was shot by commandos before he could detonate his explosives, the army said.

The military said it captured the militant's ringleader, who was known as Aqeel or "Dr. Usman." Army spokesman Maj. Gen. Athar Abbas said the militant's nickname derived from the time he spent as a guard at an army nursing school before he joined the insurgents.

The name matched that of the militant suspected of orchestrating an attack in Lahore earlier this year on Sri Lanka's visiting cricket team. Hakimullah Mehsud, the new leader of the Taliban, had claimed responsibility for that attack.

A police intelligence report from July obtained by The Associated Press on Saturday warned that members of the Taliban along with the Punjab-based Jaish-e-Mohammed were planning to attack army headquarters after disguising themselves as soldiers. The report was given to the AP by an official in Punjab's home affairs ministry.

Officials have warned that Taliban fighters close to the border, Punjabi militants spread out across the country and foreign al-Qaida operatives were increasingly joining forces, dramatically increasing the dangers to Pakistan.

The weekend strike was a stunning finale to a week of attacks that highlighted the militants' ability to strike a range of targets in different cities, seemingly at will.

On Monday, a suicide bomber dressed as a paramilitary police officer blew himself up inside a heavily guarded U.N. aid agency in the heart of the capital, Islamabad. On Friday, a suspected militant detonated an explosives-laden car in the middle of a busy market in the northwestern city of Peshawar, killing 53 people.

Before the attacks, Pakistani officials said their operations against the militants and the killing of Taliban leader Baitullah Mehsud in a CIA drone attack had left the insurgency in disarray. But the militants coalesced around his former deputy, Hakimullah Mehsud, who promised vengeance last week for the deadly airstrikes and warned that his fighters were prepared to repel any government offensive into Waziristan.

"They are well organized, and if the army takes action, they are able to hit back," former intelligence chief Jawed Ashraf Qazi said. He warned of more militant attacks ahead of an offensive: "The longer the delay, the more these actions are likely to occur."

Qazi estimated 6,000 battle-hardened Uzbek fighters are waiting in the mountains, along with thousand of local fighters from the Mehsud tribe of warriors with years of experience fighting the U.S. and Pakistan.

"The militants have had five, six years to build up infrastructure, so they're prepared," said Kamran Bokhari, an analyst with Stratfor, a U.S.-based global intelligence firm. "This is jihadist central in the country, so going in there is not going to be easy."

Yet, the recent attacks have left the government little choice but to confront the Taliban on their home turf, and the military appears better prepared than during its previous forays into the area, he said.

The army reportedly sent two divisions totaling 28,000 men to the area. They have blockaded the region, choking the Taliban's supply lines, cutting deals with local militias to prevent them from joining up with the militants and using airstrikes to take out insurgent leaders and keep the group on the run.

"This time the preparation is there. This time the resolve is there. This time pretty much everybody is on board," Bokhari said. "(The militant attacks) make it all the more clear that if you don't do this, this monstrosity that's out there in the tribal belt is not going away."