On 28 May 1926, an Army led coup d'état ended the politically instable Portuguese First Republic and established the transitory National Dictatorship, an event that led to the establishment of the New State in 1933. From 1936 on, a number of Portuguese volunteers (known as the Viriatos) offered to fight in the Spanish Civil War on the Francoist nationalist side. Many of these volunteers were officers and NCOs of the Portuguese Army, and most served mainly in elite units like the Spanish Foreign Legion and the National Aviation. Although Portugal did not officially participate in World War II, Portuguese troops fought in Timor against the Japanese invaders and had to deter a planned invasion of the Continental and Atlantic islands territories of Portugal.