I think Dad joined the US Army in 1938, and was in for eight years, getting out just before I was born in 1946. He has, I believe, buck seargent stripes which would put the year about 1939-40. David was born in 1938 and looks to be 2 years old, which makes 1940 likely as the date of this photo.
If I could only keep one photo of Dad's family I believe it would be this one. It never fails to deliver a sense of awe and emotion. And also sadness that I can't recall Grandpa Small. Oddly, I do remember (Great) Grandpa Hollar.