1508
During the Civil War Whipple first served under General Irvin McDowell then became chief topographical engineer under General  George B. McClellan  in the  Army of the Potomac  .
 top members employees: George B. McClellan, Army of the Potomac
Given a phrase that describes the relationship between two words, extract the words and the lexical relationship between them. The output format should be "relation1: word1, word2; relation2: word3, word4". 
Option: cities of residence, top members employees, members, alternate names, origin, state or provinces of residence, title of person, spouse, city of headquarters, NA, founded by, state or province of headquarters, employee of, countries of residence, country of birth, founded, subsidiaries, country of headquarters 
Text: {0} 
Answer:
 top members employees: George B. McClellan, Army of the Potomac