Kingdom of Portugal
After the Portuguese Restoration War of 1640–1668, the kingdom passed to the House of Braganza and thereafter to the House of Braganza-Saxe-Coburg and Gotha. From this time, the influence of Portugal declined, but it remained a major power due to its most valuable colony, Brazil. After the independence of Brazil, Portugal sought to establish itself in Africa, but was ultimately forced to yield to the British interests, leading to the collapse of the monarchy in the 5 October 1910 revolution and the establishment of the First Portuguese Republic.
Abolition of monarchy
World War I led to perhaps the greatest spate of abolition of monarchies in history. The conditions inside Russia and the poor performance in the war gave rise to a revolution which toppled the entire institution of the monarchy, followed by a second revolution against that government in October of the same year that executed Emperor Nicholas II and implemented a Marxist-Leninist government. The defeated German, Austro-Hungarian and Ottoman empires saw the abolition of their monarchies in the close aftermath of the war, ending the reigns of Wilhelm II, Charles I and Mehmed VI respectively. The monarchs of the constituent states within the German Empire, most importantly Ludwig III of Bavaria, Frederick Augustus III of Saxony and Wilhelm II of Württemberg, soon abdicated. During the war, monarchies were planned for Poland (Kingdom of Poland), the Grand Duchy of Finland (to have a Finnish King), and for Lithuania (Mindaugas II of Lithuania), with a protectorate-like dependency of Germany. Both intended kings renounced their thrones after Germany's defeat in November 1918. King Nicholas I of Montenegro lost his throne when the country became a part of Yugoslavia in 1918.
After the death of the last Emperor, Bogd Khan, in 1924, Mongolia became a republic. In Spain the monarchy was again abolished in 1931 by the Second Spanish Republic (1931–1939). In 1947, General Franco declared Spain a realm, and appointed Juan Carlos of Bourbon his successor in 1969. The Prince of Spain became king at Franco's death in 1975, and constitutional monarchy was restored in 1978 under him.