Brigade headquarters made a critical error in judgment by sending two battalions to attack the railway station Tarčin near Sarajevo, and the remaining two battalions on a surprise attack attempt on Konjic, thus leaving the most important objective in its area, the Ivan sedlo mountain pass, virtually unoccupied. The surprise raid on Konjic was conceived with the intention of exploiting the demoralization among the Italians, and with the hope of establishing contact with the 5th Brigade of the 3rd Division for a joint attack. But, the contact was not established, and in the night on 19/20 February, two battalions of the 1st Proletarian Brigade attacked the main target of the whole Partisan operation, the Konjic garrison, unsupported. The attack had some initial success, and the defenders were thrown back from the right bank of the river. However, since only two partisan companies managed to cross the river and enter the town center, they were easily halted by heavy mortar and artillery fire. Seeing that no progress was being made by dawn, the Brigade Headquarters cancelled the attack. The other two battalions of the brigade attacked Tarčin on the night 20/21 February. The attack coincided with the arrival of the German reinforcements from Sarajevo. As the Partisans were outnumbered, the Germans succeeded in throwing them back, and resuming their movement towards Ivan sedlo. The appearance of German units in Tarčin marked the beginning of the Weiss Mostar operation. Weiss Mostar By the third week of February the Partisans had managed to breach the Italian blockade along the Neretva River, thus compromising one of the main aspects of the operational plan for Weiss 2. Worst of all, the Partisans captured Posušje and endangered the wider Mostar area, which provided the German war industry with 10 percent of its bauxite ore needs. Since Italian troops were seemingly incapable of containing the situation, the German Command was compelled to adjust the operational plans accordingly. It was decided to deploy 718th Division immediately to the endangered areas, even before Weiss 2 was launched. The 718th Division started its attack on 19 February, with one column advancing from Bugojno towards Gornji Vakuf and Prozor, and the other from Sarajevo towards Konjic. Jablanica was the ultimate objective of both pincer arms. The column from Bugojno, named "Battle Group Vogel", consisted of the 738th Regiment (minus one battalion), the 5th Ustaša Brigade (the so-called Black Legion) and artillery.