BAGHDAD — The extension to the 172nd Stryker Brigade Combat Team’s Iraq deployment has sown chaos in the personal lives of many soldiers in the brigade’s cavalry squadron and imposed tremendous logistical burdens on the unit, problems that could have been avoided, soldiers say, if only the Defense Department had given them a little more warning. The 172nd deployed to Iraq in August 2005 and the bulk of the unit was due to return to Fort Wainwright, Alaska, early this month. But the Pentagon announced July 27 that it was extending the 172nd’s deployment for up to 120 days and...