The US military will direct a major military offensive against the Iraqi city of Mosul beginning as early as April, an official with the Pentagon’s Central Command (CENTCOM) told reporters in a conference call Thursday.

The plan calls for the US military forces in Iraq to prepare air, artillery and ground attacks against the densely populated city of 1.4 million, where an estimated 2,000 fighters affiliated with Islamic State in Iraq and Syria are reported to be entrenched.

The main body of the US-overseen Iraqi expeditionary force will be comprised of five brigades of Iraqi recruits, who will receive training at US-run camps before the operation begins, the CENTCOM official said.

US military advisors and special operations detachments will accompany the Iraqi troops, the official said.

The offensive will mark a bloody new phase of Operation Inherent Resolve, which has organized nearly 2,500 US and coalition strikes against Iraq and Syria and deployed some 2,600 US ground troops to Iraq since it began in August 2014.

Mosul fell to ISIS in June of last year, when a force of approximately 1,500 Islamist fighters routed Iraqi government forces with 15 times as many troops. Many residents, who had faced sectarian-based repression by the US-backed regime in Baghdad, welcomed the expulsion of its forces from the city. In a debacle for US policy in the region, ISIS extended its grip over at least a third of the country as US-trained and equipped security forces melted away.

Prior to the invasion by ISIS, Mosul, a city of more than a million people, had already been devastated by the US war and occupation that began in 2003. Approximately half of the city’s population, more than 500,000 people, fled as ISIS consolidated its control over northern Iraq last summer.

Washington’s plan to retake the city with some 25,000 Iraqi government troops directed and led by US “advisors” and backed by American fire-power threatens to unleash the kind of barbaric siege that was inflicted upon the population of Fallujah under the US military occupation.

The plans for US ground forces to fight alongside front-line Iraqi troops, directing strikes and providing combat support, stands in direct contradiction to President Barack Obama’s assurances last year that his administration “will not be sending US troops back into combat in Iraq.”

US and allied forces launched a fresh round of some 25 airstrikes against targets across Iraq and Syria on Wednesday and Thursday, pummeling targets near Haditha, Kirkuk, Mosul, Sinjar, Tal Afar, Al Hasakah and Kobani.

Even as the Pentagon was unveiling the plans for a siege of Mosul, the US and Turkey announced an agreement to arm and train new battalions of “moderate” Syrian “rebels” at the rate of 5,000 fighters a year.

While Washington claims that these forces are being prepared to combat ISIS, both Turkey and the so-called “rebels” are preparing another sectarian-based offensive aimed at overturning the government of Syrian President Bashar al-Assad. Whatever differences exist between Washington and Ankara, the move threatens a further escalation of the US imperialist intervention in the region and of the bloodbath in Syria.

An initial deployment of more than 400 US troops will oversee the training programs, Pentagon spokesman Admiral John Kirby confirmed, adding that the total may increase into the thousands.

The Syrian militants will receive instruction in light arms and “more sophisticated” military specialties at US-run camps in Saudi Arabia, Qatar and Jordan, in preparation for operations backed by US air and ground support. The Obama administration has already begun the delivery of pickup trucks mounted with machine guns and equipped with radios for calling in US airstrikes.

Anthony Cordesman, a former Pentagon official and leading strategist at the Center for Strategic and International Studies, has placed the coming Iraq offensive within the context of a strategy for a wave of US military operations in the Middle East, Africa and beyond, in a paper published last week, titled “Boots on the Ground, The Realities in Afghanistan, Iraq and Syria.”

Cordesman argues that the US military must learn from the experiences of the Vietnam, Iraq and Afghanistan wars, in which large US occupation forces won tactical victories while failing to enable local militaries to “stand on their own.”

The US must turn to lighter, more flexible deployments to maintain control over urban centers and vital natural resources, as central governments fragment and rebel militias increasingly dominate the hinterland, Cordesman argues.

“The ability to rapidly insert small cadres of ‘stiffeners’ like Special Forces, Rangers, and Marine combat teams may be more critical than to try to move large U.S. combat units,” he writes.

Such “high mobility strike forces” would bolster the conventional armies of “host countries” with logistical support, airstrikes and tailored use of the most advanced weapons systems, thus insuring a modicum of stability in countries of critical importance to the US government.

Indicating possibilities being considered inside the Obama administration for future interventions in Iraq and Syria, Cordesman argues that the US must develop joint forces capable of “controlling populations” and securing “key parts of the economy” amid conditions of “lasting attrition,” praising the recent success of operational, mentor and liaison teams (OMLTs) in Afghanistan in providing “forward assistance in urban warfare tactics.”