The 19th century (1 January 1801 – 31 December 1900) was the century marked by the collapse of the Spanish, First and Second French, Chinese, Holy Roman and Mughal empires. This paved the way for the growing influence of the British Empire, the Russian Empire, the United States, the German Empire, the Second French Colonial Empire and the Empire of Japan, with the British boasting unchallenged dominance after 1815. After the defeat of the French Empire and its allies in the Napoleonic Wars, the British and Russian empires expanded greatly, becoming the world's leading powers. The Russian Empire expanded in central and far eastern Asia. The British Empire grew rapidly in the first half of the century, especially with the expansion of vast territories in Canada, Australia, South Africa and heavily populated India, and in the last two decades of the century in Africa. By the end of the century, the British Empire controlled a fifth of the world's land and one quarter of the world's population. During the post Napoleonic era it enforced what became known as the Pax Britannica, which helped trade.