'5 I V r BUY 32% Anth 6 0 Site Y N H DECLASSIFIED Authority ML 3 AVE This pennant Consists as series u ARMY SERVICE FORCES h Initialstucnu UNITED STATES ENGINEER OFFICE Date P 0 BOX 1539 SANTA FE NEW MEXICO AIR MAIL mes m1 IN REPLY me To use co 12 July 1946 Subject Report of Observations at Crossroads f K To major General L R Groves Commanding General manhattan Project P 0 Box 2610 Washington 25 D C CANCELLED er AUTHORITY OF AMOND A CARPENTE as BY DATE General a Bearded USS Blue Ridge with Military 0bserver Party 12 June 1946 at Oakland proceeded to Bikini and departed ship 6 July for Kwajalein This party was composed largely of officers on staff duty in the ear Department including Ground Forces and navy Department Additional officers joined at Honolulu and a larger party essentially A A F and Navy joined at Kwajalein Included in this latter increment were three officers from Japan - two Ground and one Air On the ship enroute indoctrination sessions were held under guidance of ship s P R O covering several subjects such as ship design with Admiral Brands weather phenomena under Lt Col Russell Air Corps Instructor at Leavenworth Able Day operations under Colonel Hale Air Corps from Armyh avy Staff College etc One session in which Brown and I were asked to lead off was devoted to the Manhattan Project but I qualified the discussion at the outset to matter contained in the Report or questions thereon b The Blue Ridge traveled with the Appalachian Press and the Panamint United Nations and other observers in general assignment to the UNIT 1 3 1 of the TASK FORCE ur position during the detonation was eastward of the target fleet and was reported as 20 4 miles from its center consequently slight appreciation of the physical phenomena was gained by observers The press party was violent in criticism I did not visit any MED parties or ships in view of liaison security and transportation relations with the Navy 2 Egaliminary Observstion - a The target array in general agreed with the sketch shown in Crossroads Press Release No 46 dated 13 Why except for some minor Vessel substitutions and a general tightening up or closing in of the positions of some capital ships I estimated the Saratoga was moved 600 yards radially closer to the target ship Nevada from its position w DECLASSIFIED Authority Subject Report of Observations at Crossroads shown onrthe above noted sketch the Nagato and Pensacola 250 yards each the New York and Arkansas 300 yards the 450 yards I belieVe this shift was decided upon after early trial drops which all achieved accuracy within_500 feet of the Nevada Ga 29 June when entering and anchoring in the lagoon a good general view of the target fleet was gained and on 30 June parties were taken to observe preparations on certain target ships namely Independence Nevada and Nagato During these tours most attention was focused on the abnormal items placed on ships for observations such as Army supplies and materiel and animals 3 Detonation Observation - a Surface wind direction was quite easterly on 1 July a statement I could not verify had this wind hearing as much as 130 at the lagoon compared to the 45 normal trade wind I do not believe a change was made in the direction of approach of bombing aircraft but this factor accounts for certain ships moored bow only being caught in an attitude different from those moored bow and stern The flasht from our point of observation was but above the horizon no color other than a faint pink or salmon was observed a cloud intervened to obscure most of the mushroom effect and the lower column dissolved rapidly The heat blast and sound waves were only faintly perceptible particularly the first two and then only to an observer knowing approxi mate time of incidence The strong prevailing wind and sun conditions easily obscured the bomb phenomena b The blast occurred at 0900 hours local time and the observer vessels moved into the lagoon late the same afternoon mooring up wind between the target fleet and Bikini Island Reports Were received of sinking of the two APd's and capsizing of the Destroyer Lamson but this long range observation was limited to fires and explo- sions visible on the Independence Saratoga some transports and oil barges and general superstructure damage The following morning observers' vessels_moorings were changed to the north side of the lagoon during whiCh move the sinking of the Sakawa was observed The following day a 3-hour boat tour was made circling practically all of the target vessels and giving a very good over-all survey At this time I considered the point of detonation to left and astern of the Nevada about 500 yards later a figure of 700 yards was heard On 3 July parties were conducted aboard the Pensacola the Saratoga and the Prince Eugen and on the 4th the Nevada Arkansas and 66 position was about 500 yards forward of the Arkansas On this latter day Colonel warren came to the Blue Ridge in the afternoon to discuss radiological safety and Captain Quackenbush U S N brought film and pictures for the observers to view On the 5th Admiral Parsons Dr Sawyer Dr Bradbury Colonel Warren Captains Lyons and Drager U N S medical and others talked to assembled observers on the Blue Ridge General Nichols was present Colonel Betta JTF J2 added some_remerks on security I I DECLASSIFIED Authority Subject Report of Gbservations at Crossroads 4 - a General - nest early observations made by or reported to observers were only of a superficial nature since the full and true extent of damage was only determinable by qualified damage assay officers who were permitted to go below decks The general attitude in the Military Observer Group was to minimise damages and to limit the category to superstructure and to overlook the magnitude of combined effects of heat blast and radiation of the detonation b inkigs - 1 Attack Tgansports APA Gilliam and Carlisle were apparently closest to the high pressure region and sustained such hull damage that sinking was immediate 2 Destroyers Lamson and Anderson the first was in the vicinity of the Arkansas Was of an old design known to be somewhat dynamically'unstable and it apparently capsized immediately and sank several hours after the blast the Anderson was belieVed by Admiral Parsons to have suffered secondary internal explosions because its distance from the detonation alone did not seem to explain its rapid disappearance The Japanese cruiser Sakawa took a severe beating aft and sank the following morning before_a boarding party could get any information o Other Damage - General 1 Within the 1 000 to_l 500 yard radius I should say all outside radar-end radio gear were destroyed or seriously damaged and stacks and other light superstructure the same In the inner zone the blast pressure penetrated to interiors to affect boilers furnaces and other vital components Heat and radiation effects to vessels within 1 000 yards would have been fatal to exposed personnel and radiation effects would have been extremely serious to other personnel depending upon their degree of shielding The wave action was negligible it is doubted if this amounted to 2 feet at the island 3 miles distant 2 gxada - Serious damage aft catapult aircraft and crane destroyed main deck dished in several places and collapsed in one place probably major boiler and furnace damage Rumor that aft main gun turret shifted 3 Pensacola and Salt Lake City Crui ers and Destroyer ut 10 Hughes location was forward Nevada abo 0 yards - About the same damage as the Nevada 4 Authority soy Subject Report of Observations at Crossroads 4 Independence aircraft Carrie - The flight deck was swept clear and the island was destroyed direct blast battered the stern and buckled the flight deck Secondary'gasoline fires and torpedo explosions wrecked the interior Considerable radiation after effects which with damaging made ship uninhabitable 5 to 1J one BB - Unknown probably about equal to Nevada but close evaluation is necessary to eliminate previous damage incurred in Japan which had been quite serious i 6 Arkansas Generally the same as Pensacola above decks considerably less damage below 7 23ince Eggen and New lork -Superficial Saratogg - Nil slight burn on flight deck where QM bales ignited 9 Skate - Submarine - This vessel was moored about 100 yards in rear of Nevada and took a severe beating was said to have capsized and righted itself boarding party delayed by radiation effects 10 Concrete Barnes - Small floating dock and oil barge fairly close to high pressure zone did not appear to have sustained _any serious hull damage 11 Army Ground Forces Eguipment and Store - A gross waste of effort but probably very useful in indoctrinating personnel on the effects of atomic explosive 5 Conclusion - The Crossroads Operation was on a large scale complicated and difficult in coordination but well-run for a first operation many interested parties imbued with their own problems and desires had little appreciation of other parties involved yet coordination was achieved True results and values will only be known when consolidated report is completed A separate report by the Manhattan District on radiological effects and conclusions may be advisable to drive home points obscured by early publicity and emphasis on animals recovered alive soon after detonation fawn L E seamen Colonel C E Commanding assassins