After 20 months during which 40,000 bombs and missiles were fired at targets in Iraq and Syria, Secretary of Defense Ash Carter announced major escalations in the U.S. military campaign against Islamic State militants in the week of April 18 that will include attack helicopters and artillery systems to support Iraqi government troops.

Some of the weapons that will support Iraqi troops in the effort to retake Mosul are already in theater, namely a dozen AH-64 Apache attack helicopters that have not yet been unleashed. Soldiers to fly and maintain the rotorcraft are both in Iraq and in transit, according to Col. Steve Warren, a spokesman for Operational Inherent Resolve (OIR), who briefed reporters in a teleconference April 20 from Baghdad.

Iraqi troops will also be backed up by Marines manning high-mobility artillery rocket systems (HIMARS) from a standoff range. Carter has authorized the placement of additional advisers with Iraqi units at the brigade and battalion headquarters level

All told, the force management level (FML) – the official number of U.S. troops deployed to OIR – will increase from 3,870 to 4,087. Warren said the exact number could fluctuate because the 217 troop increase was a “doctrinal number” associated with the prescribed manning of units requested for the operation.

The “accelerants,” as the Defense Department are calling the changes to U.S. involvement in the anti-ISIL campaign, also include directly funding the Kurdish Peshmerga forces.

The enhancements to the U.S. contributions to the multi-national fight against ISIL were preceded by the deployment of B-52 Stratofortresses to the Middle East for the first time in nearly three decades. The venerable bomber scored its first hit on April 18, when one destroyed an ISIL weapon storage facility in Iraq, Warren said.

Rather than a sign of further escalation by the Air Force of its bombing campaign, Warren said the eight-engine long-range bombers will take over for the B-1 bombers that have been flying strike missions for months.

“The B-52s really are replacing the B-1s that have been flying here for almost a year,” Warren said.

B-52s have a larger payload capacity than the B-1, Warren said. Though the aircraft conjure up visions of indiscriminate carpet bombing during the Vietnam War, Warren insisted the aircraft were performing precision strike missions in Iraq and Syria.

“I know there are memories — you know — in the collective unconscious of B-52s decades ago doing very sort of less discriminate, arguably indiscriminate bombings,” he said. “I guess that’s where the phrase ‘carpet bombing’ originally came from. Those days are long gone. The B-52 is a precision strike weapon system, weapons platform. It will conduct the same type of precision strikes that we’ve seen for the last 20 months here in this theater.  So it is simply a replacement for the B-1.”