October Revolution(1917) - The second stage of the Russian Revolution of 1917, led by Leon Trotsky; the first officially communist revolution, also known as the Bolshevik Revolution.
Oliver Cromwell(1599-1658) - Military leader and politician who led an overthrow of the British monarchy in the English Civil War; established the Commonwealth of England over which he ruled as Lord Protector.
Open-Door Policy - Maintenance of equal commercial and industrial rights for all nations in China after the Opium War.
Opium War(1834-1860) - Two wars between Britain and China over a Chinese attempt to eliminate the opium trade and reduce foreign influence within its borders.
Otto von Bismarck(1815-1898) - Prime Minister of Prussia who unified Germany and became the Chancellor of the German Empire.
