The Spanish Armed Forces are in charge of guaranteeing the sovereignty and independence of the Kingdom of Spain, defending its territorial integrity and the constitutional order, according to the functions entrusted to them by the Constitution of 1978. They are composed of: the Army, the Air and Space Force, the Navy, the Royal Guard and the Military Emergencies Unit, as well as the so-called Common Corps. Spain is one of the most militarily powerful nations of the European Union (EUFOR) and Eurocorps. It also occupies a prominent position in the structure of NATO, which it joined in 1982. It also has the oldest Marine Infantry in the world and the oldest permanent military units in the world: the Infantry Regiment "Inmemorial del Rey" No. 1 and the Infantry Regiment "Soria" No. 9. History During the 15th and 16th century, Spain evolved into Europe's foremost power with the voyages of Christopher Columbus leading to Spain acquiring vast lands in the Americas. During the reign of Charles V and Philip II, Spain reached the peak of its power with the Spanish Empire spanning 19.4 million square km of the earth's surface, a total of 13%. By the mid 17th century this power had been weakened by the Thirty Years War along with financial problems, and the lack of reforms. During the 18th century the new Bourbon dynasty revived Spain's economic and military power through a series of important reforms in the armed forces and the economy, notably those of Charles III of Spain. Thanks to these reforms, Spain performed well during the war of Jenkins' Ear, the war of Austrian Succession but with mixed result during the Seven Years' War. Spain had recovered considerably by the outbreak of the French Revolution. The occupation of a great part of Spain by the French during the Napoleonic Wars resulted in the so-called war of Spanish independence, which was characterised by use on a large scale of guerrilla troops, made necessary by the war's devastating effect on the Spanish economy. Following the war, the Spanish military was in poor condition and political instability resulted in the loss of most of Spain's former colonies, except Cuba, Puerto Rico, and the Philippines. These too would be lost later in the Spanish–American War. In the 20th century, the Spanish armed forces did not intervene in the First World War (neutrality) or in the Second World War (no active