Bit of a history lesson first - At the beginning of the war companies were generally formed in the local community. Officers and non-commissioned officers were voted on and elected to these positions. Generally the more popular and knowledgeable men got these ranks. Sometimes a relative 'paid' for his son, nephew, cousin, etc to be elected to these positions.

The 5th Sergeant means that of all the Sergents in the Company he was in (Generally there were 5 or less sergeants in a company), he was the 5th highest sergent in rank in the Company (1st, 2nd, 3rd, 4th, 5th). Same with the 2nd Lt. The Junior meant that there were 2, 2nd Lts, and he was the lower in rank of the two (Captain, 1st Lt., 2nd Lt (senior), 2nd Lt (junior)).

What La Infantry Battalion was he in??

JIM T