Complex sentence: On May 16 1917, Botterell became a Probationary Flight Officer with the RNAS, where he was given the nickname "Nap" because of his supposed resemblance to Napoleon.
Split into simpler sentences: On May 16 1917, Botterell became a Probationary Flight Officer with the RNAS. Botterell was nicknamed Nap in the RNAS because of his supposed resemblance to Napoleon.