Complex sentence: Capt. Jerry Roberts was one of three original cryptographers and a founding member of the Testery, the other two were Maj. Denis Oswald and Peter Ericsson; all four were German linguists.
Split into simpler sentences: Capt. Jerry Roberts was one of three original cryptographers and a founding member of the Testery. The others were Maj. Denis Oswald and Peter Ericsson; all four were German linguists.