Although Brusilov favoured shorter bombardments, the bombardment preparation for this offensive was more than two days long, from 3am on June 4 (May 22 old style) to 9am on June 6 (May 24). This bombardment disrupted the first defense zone and partially neutralized the defending artillery. The first infantry attacks made breakthroughs at 13 points, which were soon increased in width and depth. Austro-Hungarian response to the unexpected offensive was slow and limited, believing that their existing forces and defenses would prove sufficient; instead, reserve units sent forward to counterattack often found their routes already overrun by the Russians. The Russian 8th Army, commanded by Brusilov himself just a few months before his promotion to command the Southwestern Front, achieved the greatest success, advancing in less than a week. The 7th and 9th Army achieved lesser gains, though the remaining 11th Army in the center made no initial breakthroughs. The performance of individual Austro-Hungarian units during the campaign, each raised from separate diverse societies within the Empire, was highly variable, with some units long standing firm despite the odds, like the Polish Legions at the Battle of Kostiuchnówka, whereas others readily retreated in panic or surrendered, as at the Battle of Lutsk.