While the presence and significance of the wealth of problems posed by the Czar's government should not be downplayed, it is highly likely that without the First World War - and its military problems - the regime could have continued for a number of years. The perpetual battle losses on the front line were caused by a combination of poor equipment and a lack of training and Nicholas' decision to name himself Commander in Chief led to these losses being attributed to him personally (this was especially damaging as it lead the Russian people's view of him as a divine figure, incapable of mistakes, into question). Moreover, his presence at the front left domestic affairs to the Czarina who, in addition to her German heritage, was heavily distrusted by the people for her reliance on Rasputin.
Furthermore, the Russian people were starving. Peasants being drafted for the army and leaving no one to tend their crops, combined with a poor railway system that led to full trains of food being left in isolated areas to rot bred a discontent which was exacerbated by the stories brought back from defecting soldiers of devastating battles and a starvation not helped by the appropriation of rations for the armed forces.
These conditions led to a huge increase in strike action which peaked at the end of January when Petrograd, with half of its workforce on strike, was brought to a standstill. Many of the Cossacks sent in to quell the violence ended up joining the protesters and the Duma refused to close down upon the Czars orders. When the Duma called for his abdication, the Czar, having lost the support of the military over the two and a half years, was left with no choice but to acquiesce.