 Complete the following phrase:  In the aftermath of that operation the 1st Army under Puhallo seized the bridgeheads at Sandomierz and Tarlo-Jozefow, assigned to be part of Army Group Böhm-Ermolli for the first half of 1916. It was the transferred to the Bug river region and was part of Army Group Linsingen, under the overall command of August von Mackensen, but saw little action until the end of the Russian Great Retreat, at which point the front lines became static. In the summer of 1916, Puhallo and the 1st Army were forced to withdraw during the Brusilov Offensive, and according to the general staff, the former 1st army was in the course of events dissolved on grounds of expediency and by and by divided amongst neighboring armies, the headquarters thereby becoming superfluous and was disbanded. In August, however, the 1st Army was formed once again, this time under General of the Infantry Arthur Arz von Straussenburg. Romania also entered the war on that month, and the reformed 1st Army under Straussenburg managed to hold off a Romanian 