The Royal Navy of Oman had 4,200 men in 2000, and is headquartered at Seeb. It has bases at Ahwi, Ghanam Island, Mussandam and Salalah. In 2006, Oman had 10 surface combat vessels. These included two 1,450-ton ''Qahir'' class corvettes, and 8 ocean-going patrol boats. The Omani Navy had one 2,500-ton ''Nasr al Bahr'' class LSL (240 troops, 7 tanks) with a helicopter deck. Oman also had at least four landing craft. Oman ordered three ''Khareef'' class corvettes from the VT Group for £400 million in 2007. They were built at Portsmouth. In 2010 Oman spent US$4.074 billion on military expenditures, 8.5% of the gross domestic product. The sultanate has a long history of association with the British military and defence industry. According to SIPRI, Oman was the 23rd largest arms importer from 2012 to 2016.