Yesterday I shot the thirty-first

"Dear mum! Yesterday I shot down the thirty-first, the day before yesterday the thirtieth. Three days ago I became a first lieutenant by cabinet order. - So I've gained a good six months. My squadron is doing well. I have a lot of fun with it. Lothar had his first dogfight yesterday. He was very satisfied because the enemy was shot. We call it ‘he stank’ because he left a plume of black smoke behind him. He hasn't fallen down yet, of course, because that would have been too much of a pig the first time. Lothar is very tidy and will do his job. How's Dad, and what do you think of yesterday's army report?"