Diego Garcia is a tropical, footprint-shaped coral atoll located south of the equator in the central Indian Ocean. It was used in 2001 as a base for B-1 bombers, for the bombing campaign in Afghanistan.
It now serves as the main base of operations for the Non-biological Extraterrestrial Species Treaty, aka NEST and the Autobots. Also located on the island is a burial sight for the fallen Autobots, such as Jolt and Arcee.
Revenge of the Fallen film
After their engagement with Demolisher and Sideways in Shanghai, the Autobots and NEST team return to Diego Garcia for debrief. Skids and Mudflap report to the vehicle storage hanger to upgrade their new forms while Optimus Prime headed to the command hanger and report to General Morshower. Meanwhile, Soundwave, a Decepticon communications officer, hacks a U.S. military satellite to listen their conversation in order to get the location of the AllSpark's shard.
Later, Soundwave orders Ravage to sneak into the NEST base. He releases the Microcons into a ventilation shaft, that led to the underground bunker. They were able to retrieve the shard before a small NEST team arrived after they detected a security breach. They were shortly disposed of, and the Decepticons retreated.
After the death of Optimus Prime, NEST is ordered back to Diego Garcia, but diverts to Egypt after Major William Lennox received a call from a former Sector 7 agent Seymour Simmons after Sam Witwicky learns about the Decepticons' plans from Jetfire, a former Decepticon turned Autobot seeker, and Sam has a plan to revive Optimus.
Real Life History
Officially part of the British Indian Ocean Territory the islands were home to the Chagossian people for more than a century and a half before they were expelled under an agreement between the United States and the British governments at the same time the British agreed to lease the land to build a military base. This in spite of the fact that the United States ultimately only built a base on one of the islands. The Chagossians were treated poorly when they were expelled. Leading up to the expulsion intimidation campaigns were conducted to try and make them leave, including the gassing of all the islanders' dogs. When they were finally expelled they were transported to Mauritius on a ship in poorer conditions than the horses. The Chagossian people have continued to file lawsuits in efforts to set this injustice right. Both the United States and Britain are responsible for this ongoing offense against human dignity.