Estado Novo (Portugal)
King Carlos I of Portugal confirmed colonial treaties of the 19th century that stabilized the situation in Portuguese Africa. These agreements were, however, unpopular in Portugal, where they were seen as being to the disadvantage of the country. In addition, Portugal was declared bankrupt twice—first on 14 June 1892 and again on 10 May 1902—causing industrial disturbances, socialist and republican antagonism, and press criticism of the monarchy. Carlos responded by appointing João Franco as Prime Minister and subsequently accepting Parliament's dissolution. In 1908, Carlos I was assassinated in Lisbon. The Portuguese monarchy lasted until 1910 when, through the 5 October revolution, it was overthrown and Portugal was proclaimed a republic. The overthrow of the Portuguese monarchy in 1910 led to a 16-year struggle to sustain parliamentary democracy under republicanism – the Portuguese First Republic (1910–1926).
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.