BAGHDAD » Just last month, when Western and Iraqi officials talked about the Islamic State, it was mostly to list a series of setbacks to the terrorist group: defeated in the Syrian town of Kobani, battered by a heavy airstrike campaign, forced out of a growing list of towns and cities in Iraq.

But in just the past week, the Islamic State has turned that story around. Last weekend it solidified its hold on Iraq’s Anbar province with a carefully choreographed assault on the regional capital, Ramadi. And on Wednesday, it stretched its territory in Syria into the historically and strategically important city of Palmyra.

Confounding declarations of the group’s decline, the twin offensives have become a sudden showcase for the group’s disciplined adherence to its core philosophies: always fighting on multiple fronts, wielding atrocities to scare off resistance and, especially, enforcing its caliphate in the Sunni heartland that straddles the Iraqi-Syrian border. In doing so, the Islamic State has not only survived setbacks but also engineered new victories.

"Nobody here from the president on down is saying that this is something that we’ll just overcome immediately," a senior State Department official said in a briefing with reporters Wednesday, in which the ground rules demanded anonymity. "It’s an extremely serious situation."

Within Iraq, the group’s offensive was taking shape almost immediately after the government’s victory last month in the central city of Tikrit.

Islamic State fighters took up simultaneous pressure campaigns on Iraq’s largest oil refinery, north of Baghdad in Baiji, and on Ramadi. In Diyala, the group orchestrated a prison break, a signature operation it has carried out frequently over the years and which could help restore its capability in the eastern province.

The broad scope of operations now seems to have been designed to wear out the Iraqi security forces and make sure they were dispersed when the Islamic State began its heaviest push against Ramadi this month, said Jessica Lewis McFate, an analyst at the Institute for the Study of War, a research organization in Washington that has advocated a more muscular response by the United States to the threat of the Islamic State, also known as ISIS.

In particular, McFate said the offensives had depleted and exhausted Iraq’s elite counterterrorism force, known as the Golden Division, which is highly mobile and had long fought on both fronts, in Ramadi and Baiji. The unit, which worked closely for nearly a decade with U.S. Special Forces, is seen as the most effective government force, although its numbers, compared with the regular Iraqi army and police forces, are small.

"ISIS tried to stretch the ISF as much as it could to find their breaking point," said McFate, using the abbreviation for the Iraqi Security Forces.

When the main Islamic State assault on Ramadi began late on May 14, it employed resources that had been prepared long before and were unleashed in an intense burst of violence that broke the remaining defenders.

As usual, the Islamic State opened the attack with suicide bombers, but in this case on an even bigger scale: The militants sent in 10 bomb-laden vehicles, each believed to have explosive power similar to the truck bomb used in Oklahoma City two decades ago, the senior State Department official said. Entire city blocks were destroyed.

Sleeper cells of Islamic State loyalists then rose up, according to witness accounts, helping the group quickly take control as its fighters advanced into new parts of Ramadi.

Out of fear and exhaustion, local Sunni fighters who had defended the city for nearly a year and a half left in droves last Sunday, taunted by soldiers for abandoning their land.

Staying true to its doctrine of always pushing on multiple fronts, the Islamic State has not stopped with Ramadi: It has also swept into new territory in Syria. In taking Palmyra – a relatively small and remote but strategically located desert city near the country’s geographical center – the group has for the first time seized a Syrian city from government forces, rather than from other insurgents. It attacked at a time and in a place in which government forces have been increasingly strained, exhausted and unwilling to fight for remote areas. In contrast to the barrage of suicide bombs it used in Ramadi, the Islamic State appears to have won Palmyra with a more ordinary arsenal of foot soldiers, tanks and anti-aircraft guns mounted on trucks, relying on its adversary’s weakness and the extreme fear it has managed to instill with its well-publicized atrocities.

It is probably not a coincidence that several days before its main offensive on Palmyra, the Islamic State beheaded dozens of soldiers, government supporters and their families in an outlying village and disseminated the images widely.

The group also chose its target wisely. Palmyra has a relatively small population to provide for and control, but it is a disproportionate prize. It commands access to new oil and gas fields at a time when coalition bombings have targeted many Islamic State oil sources elsewhere; has a critical network of roads; and includes an ancient site that provides endless opportunities for both propaganda and illegal antiquities trafficking.

The offensives have allowed the Islamic State to become even more deeply entrenched in territory whose desert geography and disenchanted local population work in its favor. Particularly in Anbar province, the group’s Sunni extremist fighters have been more of a native force than an invading one.

After its predecessor, al-Qaida in Iraq, was driven underground by a long and bloody U.S. military offensive late last decade, its fighters began regrouping among sympathetic Sunni tribes next door in eastern Syria.

The group survived years of battles against Syrian government forces and infighting with jihadi rivals. As it evolved, it engineered a wider hold on swaths of Syria and began plotting its return to power in western Iraq – a move the group’s founding documents held out as a priority.

That campaign began late in 2013 and led to the takeover of the town of Fallujah and other corners of Anbar. Then, in June 2014, the Islamic State made its biggest leaps into Iraq, suddenly seizing Mosul, the northern and Sunni-predominant city that is Iraq’s second largest, and driving all the way south to Tikrit.

In recent months, the group has been pushed back from some territories it seized last summer. These include cities and towns in the north near the autonomous Kurdish region and in eastern Diyala province. In Syria, the Islamic State has pulled back in recent days from the northern parts of Homs province, where it has had to compete with other groups and did not win as many locals to its side as it has in eastern Syria.

"ISIS overextended itself and is getting pushed back to areas where they can control more effectively," said Brian Fishman, a counterterrorism analyst at the New America Foundation, who has spent years studying al-Qaida in Iraq and the Islamic State. "The historical homeland for this organization is Fallujah, Ramadi, Anbar and Mosul."

With the victory in Ramadi, the Islamic State claimed the last major center of the Sunni Arab heartland, and, with the advance into Palmyra, it has expanded it.

Hassan Hassan, an author of "ISIS: Inside the Army of Terror," saw the shift as a particular challenge to the group’s enemies. "It’s really hard to conquer these areas or retake them, because in the local population there’s almost no resistance to the group here."

As it has consolidated, the Islamic State has been ruthless about beating down the Sunni tribes who have opposed it, publicizing its mass slaughters of dissidents. Among the residents who have not actively opposed the group, it has also been skillful in building up its legitimacy as a local ruling force by tapping into Sunni grievances against the Shiite government in Baghdad and the Alawite government in Damascus, Syria.

"The only solution for the situation now is national reconciliation governments in both countries, Iraq and Syria, which is impossible now," said Jalal Zein al-Din, a Syrian journalist who is part of an anti-government news agency that operates partly in Islamic State territory. "So IS is going to remain in the region, a state from Raqqa to Mosul."

In many ways, the group is staying true to a vision, laid out in documents years ago, of how it would carve out and govern a caliphate, or an Islamic state. Even as it differed from al-Qaida in its desire to hold territory, it envisioned itself as being at perpetual war with its surrounding enemies and saw its turf more as an ever-shifting zone of control rather than a place with boundaries.

In his studies of the group, Fishman has coined a term for what it has become: a "governmental amoeba."

"They conceptualize the caliphate as the people living on territory the caliphate controls, rather than a fixed geography," he said, adding, "What matters to them is commitment to the caliph."

Indeed, Ramadi was coveted in part because it had taken on great symbolic value as a place where some Sunni tribes were holding out in resistance against the Islamic State. Now, the group again has the momentum and seems more deeply entrenched than it did even before the setbacks in Kobani and Tikrit.

As with some U.S. officials, McFate, the analyst at the Institute for the Study of War, saw Tikrit, in particular, as a devastating loss that had put the group on its heels. "I thought they had lost the capability to do what they just did," she said. "The tide of the war really looked like it had shifted away from ISIS’ terms."

Things are different now, she conceded.

"Ramadi was a bigger loss for us," she said, referring to the U.S. coalition and its Iraqi partners, "than Tikrit was a loss to ISIS."

© 2015 The New York Times Company