Fort Riley ? In six months, Col. David Imhof’s troops have gone from working in a territory roughly the size and population of Topeka to an area with the same amount of ground and people as Kansas City, Mo.

Imhof, the 700 soldiers in his battalion and other officers in the 1st Infantry Division see that expanded range as a sign of progress in Iraq. His unit, the Special Troops Battalion of the 2nd Brigade, is halfway through a year’s tour.

The soldiers see other signs of progress, which to them means an Iraq in which Iraqi security forces handle more duties previously left to U.S. and allied troops. People go shopping without incident. Criminal suspects are arrested on warrants and turned over to Iraqi officials within 24 hours.

Both the new U.S. president and security agreement with Iraq took effect in January. U.S. military bases and posts are supposed to be out of Iraqi cities after June 30, clearing the way for Iraqi forces to take on greater roles.

Imhof, speaking recently through a video teleconference with reporters at the 1st Infantry Division’s headquarters at Fort Riley, says the transition so far is “seamless.”

“This is truly a historic time,” he said.

Imhof and fellow 1st Division officers are optimistic, but John Nagl, president of the Center for a New American Security in Washington, is more guarded. He views Iraq as improving but “fragile.”

Nagl said the Iraqi army is developing into a good light infantry force but still lacks artillery, armor and a big enough air force. Police units are improving but lag behind the military in development and continue to struggle with sectarian biases, he said.

“It’s a mixed bag, but the trend lines are going in the right direction,” said Nagl, a former 1st Infantry Division lieutenant colonel who trained advisers.

President Barack Obama has long advocated withdrawing U.S. troops from Iraq so they can be sent elsewhere, including Afghanistan. But a withdrawal assumes Iraq is stable and that its forces are ready to take over.

The new security agreement replaced a United Nations resolution that authorized the presence of coalition forces and spells out the role of foreign militaries in Iraq, their legal authority and when they leave.

Soldiers on the ground expect its terms to shift over time.

“As a matter of fact one of my basic statements to the state has been, ‘The only constant we will have during our deployment will be constant change,”‘ Col. Joe Martin, the 2nd Brigade’s commander, said in an e-mail from Iraq.