Brusilov, knowing he would not receive significant reinforcements, moved his reserves up to the front line. He used them to dig entrenchments about along the front line. These provided shelter for the troops and hindered observation by the Austrians. The Russians secretly sapped trenches, and in some places tunnelled, to within of the Austrian lines and at some points as close as . Brusilov prepared for a surprise assault along of front. Stavka urged Brusilov to shorten his attacking front considerably, to allow for a much heavier concentration of Russian troops, but Brusilov insisted on his plan, and Stavka relented.