Breakthrough
On June 4 the Russians opened the offensive with a massive, accurate but brief artillery barrage against the Austro-Hungarian lines. The key factor in this was the brevity and accuracy of the bombardment; the customary, protracted barrages of the day gave the defenders time to bring up reserves and evacuate forward trenches, while damaging the battlefield so badly that it was hard for attackers to advance. The initial attack was successful and the Austro-Hungarian lines were broken, enabling three of Brusilov's four armies to advance on a wide front (see: Battle of Kostiuchnówka). The success of the breakthrough was helped in large part by Brusilov's innovation of shock troops to attack weak points along the Austrian lines to effect a breakthrough, which the main Russian army could then exploit. Brusilov's tactical innovations laid the foundation for the German infiltration tactics used later in the Western Front.
Read more about this topic: Brusilov Offensive