The International Institute for Strategic Studies (IISS) is a British research institute or think tank in the area of international affairs. Since 1997, its headquarters have been at Arundel House in London.The 2017 Global Go To Think Tank Index ranked IISS as the tenth-best think tank worldwide and the second-best Defence and National Security think tank globally, while Transparify ranked it third-largest UK think tank by expenditure, but gave it its lowest rating, "deceptive", on funding transparency. Source: Wikipedia (en)