sentences:  The Hump route was so dangerous and difficult that each time a B-29 flew from India to China it was counted as a combat mission,
  
  The first combat mission by the group took place on 5 June 1944 when squadrons of the 40th took off from India to attack the Makasan railroad yards at Bangkok, Thailand.This involved a 2261-mile round trip, the longest bombing mission yet attempted during the war.On 15 June the group participated in the first American Air Force attack on the Japanese Home Islands since the Doolittle raid in 1942 when it took part in the bombing of Yawata.