Operation Enduring Freedom – Trans Sahara (OEF-TS) is the name of the military operation conducted by the United States and partner nations in the Sahara/Sahel region of Africa, consisting of counterterrorism efforts and policing of arms and drug trafficking across central Africa. It is part of the Global War on Terrorism (GWOT). The other OEF mission in Africa is Operation Enduring Freedom - Horn of Africa (OEF - HOA).

Joint Task Force Aztec Silence (JTF Aztec Silence) is the combined arms organization assigned to implement the missions and meet the goals of OEF-TS. The JTF has been part of United States European Command (EUCOM). As of September 2007, with the announcement of the new United States Africa Command, the mission will fall under the responsibility of Africa Command.

The Congress approved $500 million for the Trans-Saharan Counterterrorism Initiative (TSCTI) over six years to support countries involved in counterterrorism against alleged threats of Al Qaeda operating in African countries, primarily Algeria, Chad, Mali, Mauritania, Niger, Senegal, Nigeria, and Morocco. This program builds upon the former Pan Sahel Initiative (PSI), which concluded in December 2004 and focused on weapon and drug trafficking, as well as counterterrorism. TSCTI has both military and non-military components to it. OEF-TS is the military component of the program. Civil affairs elements include USAID educational efforts, airport security, Department of the Treasury, and State Department efforts.

The Sahara (Arabic: الصحراء الكبرى‎, Aṣ-Ṣaḥrā´ al-Kubrā, "The Great Desert") is the world's largest hot desert and second largest desert, after Antarctica. At over 9,400,000 square kilometres (3,600,000 sq mi), it covers most of Northern Africa, making it almost as large as China or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean. To the south, it is delimited by the Sahel, a belt of semi-arid tropical savanna that composes the northern region of central and western Sub-Saharan Africa.

Some of the sand dunes can reach 180 metres (590 ft) in height. The name comes from the Arabic word for desert: (صَحراء ṣaḥrāʾ [sˤɑħrɑːʔ] ( listen)).

The Sahara's boundaries are the Atlantic Ocean on the west, the Atlas Mountains and the Mediterranean Sea on the north, the Red Sea on the east, and the Sudan (region) and the valley of the Niger River on the south. The Sahara is divided into western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Air Mountains (a region of desert mountains and high plateaus), Ténéré desert and the Libyan desert (the most arid region). The highest peak in the Sahara is Emi Koussi (3,415 m/11,204 ft) in the Tibesti Mountains in northern Chad.

"Operation Enduring Freedom" (OEF) is the official name used by the U.S. government for the War in Afghanistan, together with a number of smaller military actions, under the umbrella of the global "War on Terror" (GWOT).

The operation was originally called "Operation Infinite Justice" (often misquoted as "Operation Ultimate Justice"), but as similar phrases have been used by adherents of several religions as an exclusive description of God, it is believed to have been changed to avoid offense to Muslims, who are the majority religion in Afghanistan. U.S. President George W. Bush's remark that "this crusade, this war on terrorism, is going to take a while", which prompted widespread criticism from the Islamic world, may also have contributed to the renaming of the operation.

The Operation comprises several subordinate operations:^{[citation needed]}

The term "OEF" typically refers to the war in Afghanistan. Other operations, such as the Georgia Train and Equip Program, are only loosely or nominally connected to OEF, such as through government funding vehicles. All the operations, however, have a focus on counterterrorism activities.