Two attacks on a US firebase in northern Iraq, which killed one US Marine and wounded several more, have led to revelations about a substantial escalation of the US military intervention in the war against the Islamic State in Iraq and Syria (ISIS).

The Washington Post reported Tuesday that the Pentagon has deployed more than 5,000 soldiers in Iraq, some 20 percent more than the current “cap” of 3,870 troops publicly announced by the Obama White House. The Daily Beast web site gave the total as 5,325.

The revelations of additional US forces came after ISIS attacked a Marine Corps position in Makhmour, about 70 miles south of Mosul, Iraq’s second-largest city and the largest urban area controlled by ISIS in either Syria or Iraq.

ISIS mortars slammed into the base, dubbed Firebase Bell, killing Staff Sergeant Louis Cardin and wounding several more Marines. Some of the wounded had to be evacuated out of the country in order to receive proper treatment.

Cardin, 27, from Temecula, California, was on his fifth deployment in a war zone. He had served three tours of duty in Afghanistan and one previous tour in Iraq before he was airlifted into Makhmour last month as part of the deployment of the US Marines 26th Expeditionary Unit from the USS Kearsarge, a troop carrier stationed in the Persian Gulf.

On Monday, a small ISIS unit attacked the base, home to 200 Marines, with small arms fire. They were driven off without casualties. At that point, Pentagon spokesmen acknowledged the existence of Firebase Bell, the first US-only facility to be set up in Iraq since the formal end of the US military occupation of the country in December 2011.

The Marine base sits adjacent to Iraqi Army and Kurdish Peshmerga positions in the area where the Iraqi government is assembling forces for a planned offensive against Mosul, expected later this year. The 200 soldiers at Firebase Bell operate 155mm artillery to provide long-range support for Iraqi Army and Kurdish troops and US Special Forces.

The Obama administration has classified the deployment of the Marines and many other soldiers as “temporary” in order to claim that the number of troops in Iraq is below the current ceiling of 3,870 that it reports to Congress.

Colonel Steve Warren, the top US military spokesman in Baghdad, told the press Monday, “People come through on a temporary basis and go above and below the force cap all the time, but we remain under our force cap.”

Nancy Youssef, a Daily Beast reporter, noted that Cardin’s death had revealed “a familiar, disturbing pattern in this war—one where the US military does not reveal what it is asking of troops until it has to, usually when a service member is killed. Up until Cardin’s death, the US military said its troops were only on heavily fortified bases; that its forces were not part of any offensive operations; that they were properly secured; and that frontline troops are counted in publicly released tallies of those deployed in Iraq. But Saturday’s attack revealed that none of that was accurate.”

The purpose of the official secrecy and lying is not military security. ISIS was well aware of the existence of the firebase, which it targeted with mortar shells. In any case, as one official admitted, it is hard to hide 200 heavily armed Marines stationed only 10 miles from enemy lines.

The purpose was to conceal from the Iraqi and American people what the US government and Pentagon are doing in Iraq. President Obama has repeatedly declared that he brought an end to combat in Iraq and that he would not send US combat forces back to that country. But this is what, in fact, is happening.

Iraq’s Joint Operations Command denied Monday that US Marines were involved in combat in Iraq, declaring, “There is no credibility for the rumors talking about the deployment of American fighting troops in certain sites and camps in Baghdad or elsewhere.”

Colonel Warren also denied that the deployment in Makhmour constituted a combat mission. “They won’t kind of go off and conduct any type of mission on their own,” he told reporters. “They don’t really have that capability anyways. They’re just providing coverage, right? They’re providing fire support coverage for the several thousand Iraqi soldiers and the several hundred advisers.”

Nonetheless, he admitted that the Marines had been deliberately attacked by ISIS. “I think they were targeted specifically,” he said. “We’re in a dangerous place and there’s a war going on. So we have to expect there will be attacks.”

Sergeant Cardin was assigned to the 2nd Battalion, 6th Marine Regiment. As the Wall Street Journal wrote in its report on Cardin’s death, “The transfer of a regular Marine unit into a combat zone marks stepped-up efforts by the US to combat the extremist group.”

Other press reports noted that the US government had previously claimed that ISIS used mustard gas against Kurdish troops stationed in Makhmour last year. Establishing a base for the US Marines on the same site makes nonsense of the pretense that US forces are not playing a ground combat role in the war against ISIS.

The Associated Press reported, “Makhmour is expected to become a major focus of any future offensive to gain control of Mosul, and Iraqi army reinforcements have begun arriving there in recent weeks in preparation for the operation.”

The top State Department official in the region, Brett McGurk, said the offensive had already begun, in the sense that US-backed Iraqi forces were edging toward Mosul. “It’s already started,” he told a forum at the American University of Iraq at Sulaymaniyah, in the Kurdish-ruled zone of northern Iraq. “It’s a slow, steady squeeze,” he said, adding, “It’s going to be a long campaign.”

The exposure of previously secret US military facilities in northern Iraq follows reports earlier this month that the Pentagon was operating two secret airstrips in northern Syria, inside the region along the Syrian-Turkish border controlled by the Syrian Kurdish PYG.

One airstrip, at Rmeilan, in the far northeastern corner of Syria near the Iraq border, was doubled in length in order to accommodate US cargo planes bringing supplies for the PYG and US Special Forces troops working with them. The other airstrip, near Kobani, was reported March 6 to be under construction.