Its primary clients are military forces and other security services, major defense contractors, and construction, mining, and oil exploration and production facilities worldwide.
Separately, it was also the subject of a public hearing in 2007 by the United States House of Representatives Committee on Oversight and Government Reform for its role in security contract arrangements for its staff and equipment while providing dining services to the US Army in Iraq as a subcontractor to Halliburton subsidiary Kellogg Brown & Root (KBR).
As preparations for the invasion of Iraq were being made in early 2003, and continuing through 2006, ESS was contracted by the U.S. Marine Corps, the 82nd Airborne Division, the British Ministry of Defence, the Coalition Provisional Authority, and major defense contractors Fluor, RMS, Bechtel, and most notably KBR, a subsidiary of Halliburton under the U.S. Army troop support contract called LOGCAP III to provide dining and construction services at desert bases and encampments in Kuwait and Iraq.
Over 100 Western managers and 1,500 Indian workers staffed the dining facilities, some open 24 hours per day, and lived in harsh conditions inside the camps for months at a time.
On March 31, 2004, four Blackwater security contractors were killed in an ambush in Fallujah, a city west of Baghdad, while protecting an ESS convoy en route to a Fluor construction site elsewhere.