Hello, I have a photo of my WW II veteran showing "Blue Devils" patch on his left shoulder and below that, on the arm, the "clover" patch.

I see that on his discharge papers he was a member of the 39th AAA AW Bn, Fort Bliss, Texas. He attended Artillery School and also served about 1 1/2 years overseas in Italy.

Can anyone tell me what the Blue Devils were and why it does not mention it on his discharge papers. Thanks!