(a) GENERAL DISCUSSION ![]()
Chapter I
The Strategic AreaThe strategic area involved in the combat and support operations of the Solomon Islands offensive extended from the Equator southward to the Tropic of Capricorn and from the 180th Meridian westward to the coasts of Australia and New Guinea. This over-all area, besides being entirely tropical, was oceanic. The total land mass of the small islands east of Australia and New Guinea is no greater than n the area of Celebes--or to use a more familiar example, no greater than the area of any one of the states of Washington, Missouri or Oklahoma.
The outstanding characteristic of this area is the chain of small islands extending from New Guinea to New Caledonia through the Bismarck Archipelago, the Solomon Islands, Santa Cruz Islands, New Hebrides and Loyalty Islands. These islands define the eastern boundary of the Coral Sea, including the Solomon sea north of the Louisiade Archipelago. As a series of potential air and sea bases, they constitute a barrier between Australia and North America.
This strategic area was adaptable to limited offensive operations. On the one hand, the Japanese could slowly extend themselves deeply into the South Pacific through the island chain to threaten the life-line from Australia and New Zealand to the United States. On the other hand, the Allies were provided with a route of advance toward Japanese strong points in the Western Pacific. They were also provided with an extremely advanced position from which to effect attrition upon the limited war potential of Japan. Consequently the strategic area became a theater of combat.
The strategic area was divided into two approximately equal areas by the boundary between the Southwest Pacific area and the South Pacific area along meridian 159 degrees East Longitude. This boundary passed through middle of Santa Isabel Island in the Solomons, and passed about 35 miles west of Guadalcanal Island. The Guadalcanal-Tulagi target area, wherein was fought the battle of Savo Island, lay wholly within the South Pacific area.
The threat of a large-scale overseas attack by the Japanese upon Australia and New Zealand through this area had been temporarily removed by the battle of the Coral Sea in May 1942 and the Battle of Midway in June of that year. However, the Japanese had continued to advance slowly thereafter by piecemeal penetration overland southward along the coast of New Guinea and by sea southward through the Solomons.
The relative positions of the Japanese and the Allies within this strategic area in August 1942 provided the Japanese with the more favorable military situation. The Allied positions in the south Pacific
Were but lightly held, and consisted chiefly of airfields under construction which had been hurried to a degree of readiness for limited use in the days just prior to August 7th, 1942. these airfields were located on New Caledonia, Efate, Espiritu Santo, and in the Fijis. The Japanese positions in the Bismarck Archipelago, with their principal advanced base at Rabaul, were firmly held. Their positions at Kavieng,Rabaul, Las, Salamaua, and Buka were less firmly held and were being strengthened by a major effort in the development of airfields.* In improving these positions the Japanese had extended their occupation of New Guinea as far south as Buna, had occupied Florida Island in the Solomons, and had moved into the north-central shore love Guadalcanal Island on July 4th where they had immediately begun the construction of an airfield, harbor facilities, and other installations at large at Lunga Point.
It was apparent to the Allied High command that the firm establishment of the Japanese at Tulagi and Florida Island and its airfield at Guadalcanal would seriously hamper, if not prevent the Allies from establishing themselves in Espiritu Santo and Santa Cruz,** and that therefore the Japanese positions in the Solomons were a threat to vital links in the Allied communications. It was also apparent that the Allied positions relative to the Japanese were potentially less menacing.
The positions of the Japanese and the Allies, relative to the Guadalcanal-Tulagi area in air miles.
Maramasike Estuary, Malaita (A) *** 80 miles Rekata bay, Santa Isabel (J) 120 " Kieta, Bougainville (J) 340 " Ndeni, Santa Cruz Islands (A) 365 " Buka Island (J) 392 " Rabaul, New Britain (J) 540 " Milne Bay, New Guinea (A) 565 " Espiritu Santo (A) 580 " Kavieng, New Ireland (J) 665 " Efate (A) 715 " Port Moresby, New Guinea (A) 745 " Plaines des Caino, New Caledonia (A) 790 " Noumea, New Caledonia (A) 875 " Townsville, Australia (A) 970 " Nandi, Fiji Islands (A) 1155 " There were no allied harbors in the area suitably equipped to effect major repairs to damaged ships. The docking facilities at Pearl Harbor were about 4000 miles away via Fiji. At Sydney, which was about 2000 miles away from Savo Island via Noumea, there were repair facilities for
* ComSoWesPac Dispatch 081018 which is Part Five of Dispatch 081012, July 1942
** COMINCH Dispatch 102100, July 1942
*** (A) means Allied -- (J) means Japanese--2--
cruisers and smaller craft. In an emergency, smaller harbors in the area could be used for repairs, although they were not equipped with supporting activities or base facilities. In particular, these were Saint James Bay, Espiritu Santo Island, and Noumea, New Caledonia. The best harbor site in the Solomons was at Tulagi on Florida Island, but this position was exposed tom enemy attack and was, prior to the landing on august 7th, in Japanese hands.
(b) THE TULAGI-GUADALCANAL AREA
The Battle of Savo Island was fought in the body of water lying between Guadalcanal and Florida Island which became known among Allied Forces as Iron Bottom Sound. This sound is the southeastern extremity of the Slot (New Georgia Sound). Then 100 fathom curve off Guadalcanal and Florida Islands are 20 miles apart at the western end of this Sound and close on each other to a distance of one mile to form the Sealark channel at the eastern end of the Sound.
Savo Island lies between the western extremities of Florida and Guadalcanal Islands, and is an approximately round volcanic island with a diameter of 4 miles and with its highest peak at 1675 feet. The 100-fathom curve is nowhere more than 1200 yards distant from the shore.of Savo Island, allowing un restricted navigation closed to its shores. Savo Island divides the western approaches to Iron bottom sound into two wide passages. The southerly passage between Savo Island and Cape Esperance on Guadalcanal is seven miles wide. The northerly passage between Savo Island and Florida Islands is seven miles wide.
At its eastern end, Florida Island is thirteen miles north of Guadalcanal Island and numerous shoal patches and reefs lie within the 100-fathom curves of each island on either side of Sealark channel. Through the fouled ground off Florida Island runs the Nggela channel. Through the shoals off Guadalcanal al runs the Longo channel which is three or four miles wide with depths of eighteen to thirty fathoms.
Strong tide rips are caused by the numerous shoals And irregularities in the bin the bottom between the eastern end of Florida and Guadalcanal Islands. The tidal currents set to the westward and to the eastward along the coasts of Florida and Guadalcanal Islands, following the trend of the coast line and attaining the velocity of two knots at springs.
The general depth of water in Iron bottom Sound is 200 to 400 fathoms between Lung Point on Guadalcanal and Tulagi Harbor. Tulagi Harbor is situated midway along the southern coast of Florida Island and is the principal port of the Solomon Islands. Westward of Tulagi Harbor there are no off-lying dangers, and the 100-fathom curve runs parallel with the coast about three miles offshore.
(c) WEATHER
In the Solomon Islands area there are two marked climatic seasons.
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The northeast monsoon prevails from November to March. The southeast trade wind usually establishes itself by April and lasts until October. Winds are strongest during the season of the southeast trades, averaging 10-20mph. Average wind velocities are only rarely interrupted by the passage of a tropical cyclone.It is hot throughout the year. Average monthly temperatures range from 81 degrees (F) to 84 degrees (F). Highest temperatures are recorded from November to April.
Throughout the year, average cloudiness amounts to about 5 tenths cloud cover. The cloudiest months are January, February and March. Apart from rare cyclones, other tropical depressions cause overcast skies of intermediate and high clouds. Lower type clouds prevail with local thunderstorms and rain squalls.
Thunderstorms normally occur over land during the afternoon a and over the water in the early morning. Rain squalls may occur during any season of the year. Rainfall is abundant. The months of January, February and March are the wettest. At Lunga Point, Guadalcanal the average rainfall for July is 2.70 inches. At Tulagi, average rainfall is slightly greater.
Fogs at sea level are unknown. Reduced visibility is due to heavy downpours of rain, haze, or low clouds. A particularly heavy rain squall may reduce visibility to 100 yards over a limited area. Haze is prevalent during the season of the southeast monsoon. It may render objects indistinct in visibility of 15-20 miles.*
On a cloudy night in Iron Bottom Sound, visibility has been observed to be extremely low. Rain squalls seem to form over Savo Island almost every night of the year, causing heavy rain about 2330 and clearing about 0200 as they drift slowly southeastward.** On the night of August 8th-9th, this type of bad weather did not clear up. This will be shown in the discussion of the battle itself.
* All of the above is from War Department publication SSC-677, survey of the Solomon Islands, March 15, 1943, Confidential.
** CTF 62 personal letter to Captain R.C. Parker, USN(Ret), Office of Naval History, Navy Department, Washington, D.C. dated 1948.--4--
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