The most sophisticated battlefield computer simulator is the Combined Arms Tactical Trainer. Situated at Warminster, UK and Sennelager, Germany, it is capable of training more than 850 military personnel at once in an integrated, realistic combat scenario involving vehicles, aircraft, soldiers and commanders. Simulated combat arenas of more than 10,000 km2 (3,800 miles2) are used. It was constructed for the UK’s Ministry of Defence by Lockheed Martin, and became operational on 1 September 2002.