From early August 1914, Russia and France pressured Belgrade to invade Austria-Hungary and divert troops from the Eastern and Western fronts. Despite Serbia's unpreparedness for even a defensive war, let alone an offensive, the pressure mounted as the three powers grew more and more tense. The Grand Duke Nikolai Nikolaievich even wrote a letter to Crown Prince Alexander urging him to attack. Serbian troops were armed with Russian rifles, and they wanted compensation. Belgrade resisted, claiming truthfully it had no capability to attack. Prior to the Battle of Cer, the Prime Minister of Serbia Nikola Pašić attempted to buy more time to prepare for the inevitable offensive his country would be forced into by informing the Russian Empire of his lack of pontoon bridges. He argued it would be impossible to carry out an offensive without crossing the Sava and Danube rivers. He also stated that his country lacked ammunition, and said that both "were urgently needed in the interest of an offensive and crossing against Austria-Hungary". Serbia repeatedly requested bridging material from Russia, but was refused. Field Marshal Putnik advised Pašić to stall and promise Serbia would only attack once the troops were rearmed and sufficient bridging material was obtained. This was an intelligent plan, as it would take until at least early next year to achieve this. However, the Entente refused to allow any more delay and ordered Serbia to attack. Pašić could not withstand the Entente any longer and told Putnik to attack in early September.