KIRKUK, Iraq (Reuters) - When Iraq's northern Kurdish region sent a division of troops to surround Kirkuk in February, it may have been a signal of the delicate balancing act to come when U.S. forces leave the disputed oil city.
Officially, the 10,000 or so peshmerga fighters were there to protect Kirkukis from any violence associated with nationwide protests. But their presence sparked a furious diplomatic offensive by the United States to calm tensions between the central government in Baghdad and Arbil, the Kurdish capital.
The deployment may have been a trial balloon, analysts said, to test Prime Minister Nuri al-Maliki and to warn Baghdad and Washington that U.S. troops are needed as a buffer in the disputed northern territories claimed by both capitals.
"The Kurdish military maneuver in Kirkuk in February was both a message to the U.S. to keep its troops on the ground beyond 2011 - which is a Kurdish interest - and a way of testing the resolve of the Baghdad government," said Joost Hiltermann, an analyst with International Crisis Group.
It took a month to persuade semi-autonomous Kurdistan, comprised of three northern provinces, to withdraw the unit.
"It was a lot of diplomacy in saying 'look this isn't right. It's upsetting the area. It doesn't lead to stability,'" said Colonel Michael Pappal, commander of the U.S. Devil Brigade in Kirkuk. "It showed to me that a third party was necessary for that to happen."
Eight years after the United States ousted Saddam Hussein, Iraq is still building its police and army to battle a lethal Sunni Islamist insurgency and Shi'ite militias within, as well as defending against external threats.
As violence ebbs, Kirkuk and other disputed northern areas are considered potential flashpoints for future conflict in a country hobbled by ethnic, religious and political strife.
The late February incursion was no spur-of-the-moment decision and prompted a quick response from the Americans, who told Kurdish commanders their soldiers would not be allowed into Kirkuk, U.S. military officials said.
"You don't send a division across a border without a lot of planning and preparation ... it takes a while to put an army on the road and that's what they did," said Lieutenant Colonel Joe Holland, a U.S. commander in Kirkuk.
The unit was 12,000 strong, a Kurdish official told Reuters, while the U.S. military estimated it at 8,000-9,000. Sources said the Kurds had AK-47s, artillery and armored vehicles.
CLOSE TO BLOWS
Holland said it was the third time in 20 years the Kurds had moved into the Kirkuk area; the first in 1991 after the invasion of Kuwait and the second in 2003 when Saddam was ousted.
Maliki's government demanded the peshmerga withdraw and the Kurdistan Regional Government at first refused, escalating tensions. Iraqi and Kurdish troops have come close to blows in the past two years as Baghdad tightened its grip on Kirkuk.
Iraqi officials said the incursion was illegal. Officially, the city -- which by some estimates sits atop 4 percent of the world's oil reserves -- is secured by central government forces.
"The effect was a significant schism in the relationship between us and the Kurds," Holland said.
Kirkuk has suffered huge population upheavals in recent decades, from Saddam's "Arabization" campaigns to more recent moves by Kurds to reclaim parts of the city.
"They were sending a message to the central government, saying 'we can enter Kirkuk any time and you cannot stop us,'" a senior Iraqi Defense Ministry official told Reuters.
The official said the KRG would not invade Kirkuk after the U.S. leaves but would seek to displace Arabs. He said the Kurd population had soared from 150,000 to 350,000 since 2003.
The peshmerga, however, represent a formidable challenge to the Iraqi army. The Kurds have 100,000 troops, better weaponry and experienced leaders, the official said.
"After 2003, they captured the former Iraqi army tanks. About 4,000 tanks left by the former Iraqi army in the streets and cities disappeared, and our investigations indicate that the Kurds have most of them and Iran got the rest," he said.
The peshmerga deployment served notice that without the neutral buffer of U.S. forces, the Kurdish region might "feel compelled to use military muscle to defend its interests," said Wayne White, an analyst with the Middle East Institute.
"So, while a signal that the KRG will not tolerate any perceived trampling of its interests in Kirkuk, this deployment also was meant as a reminder to both Washington and Baghdad that greater consideration should be given to the prolongation of a more meaningful U.S. presence," he said.
But because Maliki, perhaps calculating that the Americans would pressure their Kurdish allies to withdraw, did not offer a serious challenge, the deployment was not an effective trial run for securing Kurdish control of Kirkuk, Hiltermann said.
"This will have to wait till the time when U.S. troops will no longer be there," he said. "At that point, all bets are off and tensions could easily escalate, intentionally or inadvertently, to a bigger conflict, at least as long as the dispute between Baghdad and Arbil remains unsettled."
(Additional reporting by Suadad al-Salhy; Editing by Jon Hemming)