Twelfth in the series of studies on particular combat operations, "St-Lo" is the story of a corps in First Army during the bitter July battle that led up to and made possible the great breakthrough from the Normandy beachheads. This was the period of the most intense hedgerow fighting. XIX Corps' part in it has been chosen to illustrate this type of combat. The records of other First Army units in this operation have been covered only in outline. "St-Lo" is one of a series of fourteen studies of World War II operations originally published by the War Department's Historical Division and now returned to print as part of the Army's commemoration of the fiftieth anniversary of that momentous clash of arms. These volumes, prepared by professional historians shortly after the events described, provide a concise summary of some of the major campaigns and battles fought by American soldiers.