The plot of Mark Helprin's novel The Oceans and the Stars imagines the United States at war with Iran. At one point the heroes of the book end up in the Indian Ocean searching for an Iranian vessel, ultimately battling a force the US captain refers to as the NEDSA, the naval arm of the Iranian Revolutionary Guard Corp (Sepah-e Pasdaran-e Enqelab-e Eslami, aka the IRGC, also referred to as the Pasdaran or the Sepah).
Iran has two independent military organizations. The first, the Islamic Republic of Iran Army, Artesh-e Jomhouri-ye Eslami-ye Iran or simply Artesh, pre-dates the 1979 Iranian Revolution and is responsible for defending the country's borders against external threats and maintaining internal order. It's considered a conventional military force, and has traditional army, navy, air force and air defense branches. Its role is similar to what Americans think of as a classic armed services organization.
The other is the IRGC, formed after the Revolution during a time ...