Help with terms in India List

[Nepper]

There are some term used in the India List that I need help in defining.  I see British officers attached to Indian units with descriptions such as "Double Company Officer", "Wing Commander" and "Wing Officer" but I can't find definitions anywhere.  Can anyone oblige?  TIA

[Steven Broomfield]

'Wing' would probably refer to the system of dividing a battalion into two halves (or 'wings')while on operations, command being given to the senior majors; 'Double Company' might refer to two (of eight) companies being combined to create one administrative unit) or (during the Great War) the larger companies created by amalgamation of two companies when the Indian Army adopted the new 4-company system.