Before the US and Israeli attacks against Iran and Iran's retaliation, you'd be excused if you didn't know that the US has a plethora of military bases in the Middle East – that have now been targeted by Tehran – and around the world. As it is highly topical, today we explore the history, rationale and breadth of the US military presence overseas.

Early history

Before the end of the 19th century, the US was largely isolationist and still heeding George Washington's warning not to become entangled in overseas wars. But, after it fought its own Civil War in the 1860s, finally uniting the country, and wiping out the Native Americans in the West in its quest for Manifest Destiny in the 1870s, the US started to become another expansionist power.

Theodore Roosevelt, the 26th President, was one of the central figures in the story. He almost single-handedly started the Spanish-American War (1898) as a mere Assistant Secretary of the Navy, before resigning to become a Lt Col in the "Rough Riders," a voluntary cavalry unit he founded so he could fight in the war he helped start.

The US quickly defeated the declining Spanish empire and got its first real taste of imperialism, with Spain ceding the territories of Guam, Puerto Rico and the Philippines. In addition, Cuba, another Spanish territory, was put under US occupation before independence in 1902, with the US holding onto a slice of the island that is its oldest and perhaps most continuous military base, Guantanamo Bay. It also established bases in Guam and the Philippines to protect its newly acquired territory.

Despite entering the imperialist scramble, the US still mostly maintained its isolationist streak until the start of WWII. In 1940, with the British in desperate need of supplies, President Roosevelt (Franklin, not Teddy this time) negotiated the Destroyers-for-Bases agreement. In exchange for some old ships, the US gained 99-year leases of British bases in the Western hemisphere, including Newfoundland, Bermuda, the Bahamas, Jamaica, St. Lucia, Trinidad, Antigua and British Guiana (now known as Guyana).

Having a US military presence in the Caribbean ensured the US could protect the Panama Canal (vital to its West coast trade), its Eastern seaboard and the Mississippi River Delta at New Orleans, where vast quantities of goods from the US heartland were shipped abroad via the Gulf of Mexico.

In mid-1941, despite not having entered the war, the US also took over the British occupation of Iceland (with consent from Iceland) to monitor and combat Nazi forces in the North Atlantic.