What do these East India Company military abbreviations mean? I have the service record from the India Office of Records for my 3rd great grandfather who served with the Bengal Artillery of the East India Company. While I can get the "gist" of his record I am curious to know what "G.O", "G.O.C.C." and "U.1st. A. G.O." refer to as in "Admitted to the service G.O. 27th August 1811 Arty. Regimental Orders of 8 instant appointing him temporary adjutant to 3rd Batt. Artillery confirmed G.O.C.C. 12th January 1820. Leave from 15th December to 1st February 1821 U.1st A. G.O. 12th December 1820 ....." and so on.

India Office Family History Search within the British Library is an excellent starting point for research involving British ancestors in India (or Anglo Indian ancestors). For this particular question, the Abbreviations and Glossary page is invaluable.