Hi Rainer, I can see why clarifying U-boat patrols as a low priority, and I originally set out just to do the type IXB, however, that done during a lull in new data for the IXB I naively looked at a few others and was quite surprised how many had false starts with minor mechanical problems before completing their patrol. Then as you mentioned there is the various other reasons which come in to the equation. U212 being one boat where I am at a loss, listed here with fifteen patrols, when counter checking dates e.t.c with Ubootarchiv, ten match, while patrol number 10 they list as 'Deep dive tests'. While patrols numbers 11 and 12, as well as patrols 14 and 15 are grouped as pairs, each being directed against 'Normandy invasion shipping'. I would therefore, as time allows appreciate your advise with this. Regards John