WASHINGTON --Documents captured from Iraqi insurgents indicate that some of the recent fatal attacks against U.S. helicopters are the result of a carefully planned strategy to focus on downing coalition aircraft, one that U.S. officials say has been carried out by mounting coordinated assaults with machine guns, rockets and surface-to-air missiles.
The documents, which are said to have been drafted by al-Qaida in Mesopotamia, show that the militants were preparing to "concentrate on the air force."
The contents of the documents are described in a U.S. intelligence report that was reviewed by The New York Times. Seized near Baghdad, the documents reflected the insurgents' military preparations from late last year, including plans for attacking aircraft using a variety of weapons.
Officials say they are a fresh indication that the United States is facing an array of "adaptive" adversaries in Iraq, foes who are likely to step up their attacks as U.S. forces expand their efforts to secure Baghdad, the Iraqi capital.
"Attacks on coalition aircraft probably will increase if helicopter missions expand during the latest phase of the Baghdad Security Plan or if insurgents seek to emulate their recent successes," says the intelligence report, which analyzes the recent helicopter crashes.
The U.S. military has said that seven helicopters have been downed since Jan. 20, a figure that exceeds the total number of coalition aircraft shot down in 2006.
After downing the helicopters, the insurgents often laid ambushes for the U.S. ground troops they expected to come to the rescue, sometimes using roadside bombs that they placed in advance. U.S. troops were attacked in five instances in which they rushed to the scene of aircraft that had been shot down, military officials said.
The intelligence report supports the concerns expressed by a U.S. general this month that militants were adapting their tactics in an effort to step up attacks against helicopters. From December to January, the number of antiaircraft attacks rose by 17 percent, according to a U.S. military report.
Insurgents in Iraq have boasted about the helicopter downings and posted video footage of some of the wreckage on Web sites operated by militants.
While al-Qaida in Mesopotamia has claimed that it has "new ways" to shoot down the aircraft, some American analysts think that they are probably not employing new types of weapons but are making more effective use of arms already in their inventory.
The insurgents try to plan their attacks by studying flight patterns near U.S. bases and along supply routes, according to the intelligence report. In several recent helicopter downings, the attackers used a variety of weapons, including shoulder-fired surface-to-air missiles, heavy machine guns, rocket-propelled grenades and unguided rockets that cannot be diverted by the flares helicopters disperse to fool heat-seeking systems.
Al-Qaida in Mesopotamia, which the intelligence report says leads the insurgent group known as the Islamic State of Iraq, has claimed responsibility for shooting down three of the helicopters. Those were the helicopters downed near Taji, Karma and in Diyala province.
While the captured documents point to careful planning, it is not entirely clear whether this is an effort by some of the militant commanders in those areas or a nationwide strategy by the group.
Maj. Gen. James E. Simmons, a deputy commander of the U.S.-led multinational force in Iraq and an Army aviator, told reporters last week that multiple weapons systems had been used against U.S. troops before, in attacks south of Baghdad last year. "This is not a new tactic," Simmons said. "But it is the first time that we have seen it employed in several months."
"We are engaged with a thinking enemy," he added. "This enemy understands based on the reporting and everything else that we are in the process of executing the prime minister's new plan for the security of Baghdad. And they understand the strategic implications of shooting down an aircraft."
He said that U.S. commanders in Iraq have met to consider how to counter the shift in insurgent tactics, but he declined to discuss specifics.
Simmons said the U.S. military has not concluded that a single militant cell is behind the attacks. Also, some of the attacks have been described by U.S. intelligence as opportunistic, meaning insurgents are simply firing at helicopters when they see them.
U.S. helicopters are being used extensively as U.S. troops try to avoid the bombs hidden along roads. Low-flying aircraft are also vulnerable when they pass over urban areas. In 2005, U.S. Army helicopters flew 240,000 hours. This year, Army helicopters are expected to fly more than 400,000 hours, military officials said.
Simmons had a firsthand look at opportunistic tactics Jan. 25 when he was in one of a group of helicopters that was fired on near Hit in Anbar province. In that attack, a Black Hawk helicopter in the group was stuck by automatic weapons fire after the helicopters flew near some militants who appeared to be removing arms from or bringing them to a weapons cache.
The damaged Black Hawk helicopter was forced to land. The helicopter Simmons was in landed and picked up the crew, and the Marines sent a quick-reaction force to protect the aircraft, which was later brought to the U.S. base at Asad.
"I've got firsthand knowledge on that one," Simmons said. "We stumbled upon them, and they engaged us with what they had, and they got lucky."
Military officials say another opportunistic downing was the attack on an Apache helicopter near Najaf on Jan. 28 that killed both crew members. It occurred when the aircraft was sent to reinforce U.S. and Iraqi troops. The officials also noted that the attack was the only recent instance in which a Shiite group - in this case, the Soldiers of Heaven - was responsible for shooting down a helicopter.