No lo traduciría literalmente pues tal cargo no parece existir y ya te redondeo la idea en el contexto de lo que significa en Turquía

http://www.meandertravel.com/turkey/turkey.php?details=atatu...
FOUNDER AND THE FIRST PRESIDENT OF THE TURKISH REPUBLIC
Ataturk was born in 1881 at the Kocakasim ward of Salonika, in a three storey pink house located on Islahhane Street. Between 1905 - 1907 he was stationed in Damascus with the 5th. Army. In 1907 he was promoted to the rank of "Kolagasi" (senior major) and was posted with the III rd Army

Ahora veamos que es Kolagasi en Turquía: Kolağası (also written as Kol Ağası, Kol Aghasi) was a military rank of the Ottoman Army. It corresponds to a Senior Captain (modern Turkish: Kıdemli Yüzbaşı)[1] or an Adjutant Major.[2] Kol Ağası is a compound word composed of Kol (column in Turkish) and Ağa (chief in Turkish).

Es un rango entre capitan y mayor, es decir entre Senior Captain o Adjuntant Mayor.

No podemos sacar rangos de la manga que no existen o que simplemente no se manejan. Hasta donde mi experiencia me dice "entre Capitán y Mayor" no suelen encontrarse rangos intermedios en las fuerzas militares de los países. Para no inventar grados que no existen te sugiero mi traducción