How was chinggis khan able to unify and create such a strong war machine? what was he able to build and whay did he have to create?

Genkhis Khan created Mongol empire which was world's second largest empire by area. While Mongol conquests were exceptionally bloody, after the conquests came , a century plus of relative peaces and prosperity. Large empire under stable rule eased communication (led to creation of world's first postal system) and unified administration helped to create commerce.