WASHINGTON — Several dozen U.S. special forces troops flew into Syria last month in a bid to rescue several Americans held by the Islamic State, including journalist James Foley, but they pulled out after discovering that the captives had been moved, senior U.S. officials said Wednesday.One U.S. soldier was wounded.The raid, which took place over the July 4 weekend, is the first known instance of U.S. troops entering Syria since the brutal civil war erupted there in mid-2012. The disclosure offered insight into how much intelligence the United States had gathered on the whereabouts of Foley and the undisclosed number of other Americans held by the Islamic State.According to an account provided to McClatchy, the media organization that owns the Star-Telegram, by an Islamic State operative, the raid targeted a militant base in northern Raqqa province named Camp Osama bin Laden and left five militants dead and many others wounded.The Obama administration disclosed the raid a day after the Islamic State posted an online video showing Foley, 40, a freelance photojournalist from Rochester, N.H., being beheaded in retaliation for U.S. airstrikes launched this month against the extremists in northern Iraq. Militants warned other killings would follow.President Barack Obama authorized the U.S. operation after intelligence pinpointed the location of the prisoners, senior administration officials said in a briefing to reporters. The briefing was held after McClatchy and several other news organizations learned of the raid and began asking Pentagon officials for details.“The president authorized action at this time because it was the national security team’s assessment that these hostages were in danger with each passing day,” Lisa Monaco, an assistant national security adviser, said in a statement issued by the White House after the briefing. “The U.S. government had what we believed was sufficient intelligence.”The raiding force included members of nearly every U.S. military service and was supported by helicopters and fixed-wing aircraft and surveillance aircraft. The force flew into the site on helicopters, conducted a search on foot and then left after discovering that the hostages were no longer there, the officials said.The U.S. force came under fire as it flew out and shot back. One special forces soldier was injured aboard a departing aircraft, said the senior administration officials, who declined to be identified under the ground rules for the briefing.“We do believe that there were a good number of ISIL casualties,” one senior administration official said, using the U.S. government acronym for the Islamic State.The senior administration officials declined to disclose how long the raiders were on the ground or where the operation took place.Many experts believe that Foley and other foreigners were being held in northern Syria, large parts of which were overrun in 2013 by the Islamic State. The al Qaida spinoff established its headquarters in Raqqa, the provincial capital of a Syrian province of the same name, and used it as a springboard for the lightning offensive it launched in Iraq in June.Start of a ‘sacred war’The U.S. disclosure corroborated an account provided to McClatchy by the Islamic State operative, who declined to be identified.The operative contacted a McClatchy correspondent based in Turkey. He said that helicopter-borne American forces had flown into the al Ikairsha area of Raqqa province and stormed the Islamic State base.The Islamic State viewed the attack as “strange” and saw it as the start of a “sacred war” between the group and “the grandchildren of apes and pigs,” he said, referring to passages in the Quran.There may have been a second U.S. attack that same day, this one a missile strike on an Islamic State base in eastern Syria, according to an exiled Syrian journalist.In a report he posted on Facebook quoting a resident of the area, the Syrian journalist, Abdulnaser Al Iyed, said that the base was in a two-story building in the town of Ma’adan, west of the provincial capital of Deir al Zour. Iyed is from Deir al Zour and now lives in Istanbul.More hostagesTwo officials authorized by the White House to speak anonymously to a small group of reporters declined to specify the number or identity of Americans being held alongside Foley. They are believed to number at least four, one of whom, freelance journalist Steven Joel Sotloff, also appeared in the Foley video, as the executioner warned that “the life of this American citizen, Obama, depends on your next decision.”The failed operation “was conducted by a joint force with virtually every service represented,” one of the senior officials said, including “special operators and aircraft both rotary and fixed wing,” with surveillance aircraft overhead.That official said that there were a “good number” of militant casualties at the site, but that one U.S. service member received a “minor injury when one aircraft did take some fire.”The two senior officials declined to specify the location of the raid, whether the hostages had ever been there, the specific U.S. units that had taken part in the operation or how long they were on the ground. “It wasn’t an extraordinarily long period,” one said.This report includes material from The Washington Post.