Simplify the following text for a Grade 10 native English-speaking person.
Original: Field Marshal Douglas Haig , 1st Earl Haig , KT , GCB , OM , GCVO , KCIE , ADC , also commonly known as ` Butcher Haig ' , ( 19 June 1861 â `` 29 January 1928 ) was a British senior officer during World War I. He commanded the British Expeditionary Force ( BEF ) from 1915 to the end of the War , he was notable as the British commander with the most casualties under his command , in total 2 million British soldiers , it was for this record he was dubbed `` Butcher Haig '' .
Simplified: Field Marshal Douglas Haig KT , GCB , OM , GCVO , KCIE , ADC , ( Edinburgh , 19 June 1861 â `` London , 29 January 1928 ) was the senior British Army commander in World War I.