Complex sentence: The cause of this war was Yuan Shikai's proclamation of himself as Emperor; only 3 years earlier, the last Chinese dynasty, the Qing Dynasty, had been overthrown and a Republic of China established in its place.
Split into simpler sentences: The cause of this war was Yuan Shikai's proclamation of himself as Emperor. Only 3 years earlier, the last Chinese dynasty, the Qing Dynasty, had been overthrown and a Republic of China established in its place.