From “The Imperial Japanese Navy”, Paul S. Dull, 1978 United States Naval Institute, and “History of United states Naval Operations in World War II”, S.E. Morison, Little Brown & Company 1975
According to both Morison and Dull the Sanuki Maru was damaged by shore battery fire on 23 Dec. No mention of any US air attacks on 27 January is made in either book.
Neither Morison or Dull make any mention of the Chitose being damaged by air attacks in this time period.
Kamikawa Maru and Kimikawa Maru: Likewise no mention in Morison or Dull.
Akitsushima: Morison, Vol 5, Pages 117-118
On 1 September a Flying Fortress on a scouting mission chanced upon seaplane carrier Akitsushima north of Choiseul and showered her with a salvo of bombs which failed to hit but did slight damage as near-misses.
Sanuki Maru: No mention in Morison or Dull.
Kunikawa Maru: No mention in Morison or Dull.
Ashigaga: Pg 31 Dull
A B-17, piloted by Captain Colin P. Kelly, attacked the heavy cruiser Ashigara of the Northern cover force on 10 December. Captain Kelly, who did not survive the mission, reported by radio before his plane went down that he had hit and set afire a Kongo class Battleship (later claimed by the USAAFFEE to be the Haruna), but the Ashigara was not hit.
Appendix A in Dull’s book lists the fate of every Major IJN warship (destroyers and larger ships). In this list, I could only find only one ship in the open ocean that was sunk by USAAF level bombing, the DD Mutsuki. Here is the description of the Mutsuki’s sinking from Morison, Vol 5, pg 105. When the incident occurred the Mutsuki was rescuing survivors off the Kinryu Maru.
At 1015 eight Flying Fortresses from Epiritu Santo appeared over Tanaka’s force. Commander Hatano, Mutsuki’s skipper, glanced up at them and casually returned to his rescue work. Consequently, when the “Forts” let go a pattern of bombs, his destroyer was dead in the water. After three bombs had struck, she was dead under the water. Commander Hatano emerged, dripping, to remark quaintly, “Even the B-17s could make a hit once in a while!” He claimed that his ship was the first to be hit by Horizontal bombers during the war.
Some observations: Snorkey has not provided one example of ship actually being sunk by level bombers except in the case of ship previously mined and thus probably unmoving or moving very slowly. In the only example I could find of an IJN warship being sunk by level bombers, it was unmoving. The USAAF claimed many ships both sunk and damaged from their level bombing attacks. Claims of a ship sunk by level bombers were later disproved when the ship in question was located again. Erroneous damage claims however are not disproved by a later sighting of the ship since it may have theoretically been repaired.
For perspective the USAAF claimed the following results against the IJN at Midway: Hits on 3 carriers, 1 cruiser, 1 battleship or cruiser, 1 destroyer and 1 large transport. (Morison Vol 4, pg 159) In actuality the USAAF missed with every single bomb. From the same page:
The A.A.F. pilots, of course, believed what they said, since it is almost impossible for a high-level bomber to distinguish between a hit and a near miss.
Hooligan