Four thousand members of the Pennsylvania Army National Guard, including about 150 based in Chester County, have received word that they will mobilize on Sept. 19 for eventual deployment to Iraq around the end of the year.

The men and women of the Guard's 28th Division 56th Stryker Brigade were put on alert last October, and have been expecting the official mobilization order that arrived a few weeks ago.

One of the brigade's units, Bravo Company of the First Battalion, 111th Infantry, is based at armories in West Chester and Phoenixville.

The Sept. 19 mobilization will mark the beginning of the soldiers' 12-month deployments. The anticipated date for deployment overseas has not been released; the brigade will first head to Camp Shelby, Miss., on Sept. 22. There, they will undergo mobilization training to become familiar with current conditions in Iraq.

"If there's been any adaptations by the opposing forces, we get a chance to practice the counteractions to that," said Lt. Col. Mark O'Hanlon, commander of the First Battalion, 111th Infantry. "We'll be trying to stay two to three steps ahead of what the insurgents are doing."

The 1st battalion will also travel to Camp Shelby at the end of this month for three weeks of annual training in late June. Its Stryker military vehicles - the fast, powerful combat machines for which the brigade is named - are there already.

O'Hanlon said it was possible that, after the brigade reports to Camp Shelby in the fall, the soldiers may be able to return home for Christmas with their families, and then deploy to Iraq from Fort Dix.

There are seven Stryker Brigades in the Army, but the 56th is the only reserve brigade. It will likely replace another Stryker unit currently in Iraq, where its soldiers will be handle full-spectrum operations, including high-intensity conflict, humanitarian support and stability operations.