With thousands of US ground troops reportedly on their way to the Middle East, speculation is increasing that they may be assigned to take Iran's Kharg Island, a key fuel hub in the northern Persian Gulf. However, other Iranian islands in the gulf may be more important to securing the safe passage of ships and naval vessels through the Strait of Hormuz. Seven of these islands, Abu Musa, Greater Tunb, Lesser Tunb and Hengam, Qeshm, Larak and Hormuez, form what researchers at Sun Yat-sen University in Zhuhai, China, call Iran's "arch defense". The researchers suggest that removing Iranian military positions on these islands would make them easier for US warships to enter the Gulf. There is no timeline for possible US amphibious assaults on any of Iran's islands.