Iran's fortifications on small islands near the Strait of Hormuz boost its power to control the key waterway, and reopening shipping there might require U.S. or allied forces to capture some of those same dots of land.
The importance of the islands such as Kharg, Qeshm and Abu Musa is increasingly coming into view as Iran causes an economic crisis by blocking most oil tankers from transiting the strait.
Navigation through the Hormuz Strait requires you to follow a certain route, says Yossi Kuperwasser, former head of Israeli military intelligence research and now director of think tank Jerusalem Institute for Strategy and Security.
This route goes between islands that are controlled by Iran.
Tehran has called its 19 islands in the 100-mile strait aircraft carriers, installing radar systems, airstrips and fuel depots, missile systems and naval launches for submarines and fast-attack boats.
Unlocking the strait promises to be the next phase of the war, either through a negotiated peace agreement or a military operation.
An amphibious assault ship, the USS Tripoli, arrived in the Middle East over the weekend ferrying elements of the 31st Marine Expeditionary Unit, which is specifically trained for operations such as taking control of islands in hostile territory.
