With PERSON@1 overthrown , PERSON@2 , with his assistant PERSON@3 and friend , the mathematician PERSON@4 , fled LOCATION@1 for LOCATION@2 , where he was employed as a military architect and engineer , devising methods to defend the city from naval attack .

PERSON@2 left LOCATION@1 with his servant PERSON@3 and a friend , PERSON@4 , who was a mathematician .
