A U.S Air Force KC-10 refuels an F-22 Raptor fighter jet after strike operations in Syria, Sept. 23, 2014. The United States and partner nations launched the largest combined single day of airstrikes on Iraq and Syria on Tuesday, striking 13 times in Iraq and 11 more in Syria. (U.S. Air Force photo by Maj. Jefferson S. Heiland)

The United States and Great Britain launched 24 more airstrikes in Iraq and Syria, defense officials said on Tuesday, making it the biggest day yet in the air war against the Islamic State militant group.

Eleven airstrikes each were conducted in Iraq and Syria by U.S. warplanes, officials with U.S. Central Command said in a statement. Separately, British officials said they conducted their first two airstrikes in Iraq since joining the military campaign. Combined, the action surpassed Sept. 23 — the first with strikes in Syria — as the day with the most airstrikes in the two countries.

Fourteen airstrikes were launched in Syria on Sept. 23 as the U.S. and partner nations began their air war there, and four more were carried out at the same time in Iraq. Eight further strikes were carried out that day in Syria, but they came from 47 Tomahawk missiles launched by the U.S. Navy from ships in the Persian Gulf, rather than warplanes. Most of those were aimed at the Khorasan group, which U.S. officials said is an al-Qaeda affiliated group that was planning “imminent” attacks against U.S. and Western targets.

Rear Adm. John Kirby, the Pentagon press secretary, said Tuesday that the latest strikes in Iraq and Syria show that the United States will continue to go after the Islamic State. But he warned that the campaign will take time, and that the militants still pose a threat.

“We’ve been pretty honest about the fact that military action alone will not win this effort, but that shouldn’t be taken as an admission of ineffectiveness, and one of the ways we know we’re having an effect is precisely because the terrorists have had to change their tactics and their communications and their command and control,” Kirby said.

“No one said this would be easy or quick, and no one should be lulled into a false sense of security by accurate airstrikes,” he added. “We will not — we cannot — bomb them into obscurity.”

The latest strikes in Syria were carried out in four locations: near Dayr ar Zawr in eastern Syria (two strikes); near Sinjar, Iraq, on the border of northeastern Syria (five strikes); near Mazra al Duwud near the Turkish border (three strikes); and northeast of Aleppo (one strike).

A series of YouTube videos, from the United States Central Command, shows four airstrikes against the Islamic State on three separate dates. The video includes strikes made on a weapons storage facility in South Milibya, Syria, and on a rebel-held building east of Al Hasakah, Syria. (United States Central Command)

The bombing near Dayr ar Zawr destroyed a an armored vehicle and an armed vehicle controlled by the militants. Near Sinjar, the strikes hit an artillery piece, a tank, three armed vehicles, two unnamed facilities, an observation post and four fighting positions, defense officials said. The strikes near the Turkish border reportedly destroyed one artillery piece and damaged another, and destroyed two rocket launchers. Near Aleppo, four building occupied by militants were destroyed, officials said.

In Iraq, seven U.S. airstrikes were launched in northwest Iraq, hitting one armored vehicle, two transport vehicles, and five armed vehicles. Two more airstrikes were launched near the Mosul Dam, taking out a militant fighting position and an armed vehicle, U.S. military officials said. Northwest of Baghdad, another airstrike reportedly destroyed an armed vehicle, and a strike west of Fallujah, in western Iraq, hit an Islamic State checkpoint.

British defense officials said Royal Air Force Tornado GR4 fighters carried out two airstrikes in northwest Iraq to assist Kurdish troops under attack by militants. In the first, they destroyed an Islamic State position with a bomb, officials said. In the second strike, an armed pick-up truck in the same area was taken out with a Brimstone missile fired by a Tornado jet.

The United States has now launched 233 airstrikes in Iraq since beginning its air campaign against the Islamic State there Aug. 8, according to a Washington Post database maintained by Checkpoint. At least 62 more airstrikes have been launched by the United States and its Arab partners in Syria. No Arab nations were involved in the strikes announced Tuesday. Kirby attributed that to timing and maintenance.

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