Chapter IV: Establishment of the Perimeter and Battle of the Tenaru
THE EXISTENCE OF THE FLEET MARINE FORCE in 1942, together with the leadership and amphibious technique it had produced, made Guadalcanal
Chapter IV: Establishment of the Perimeter and Battle of the Tenaru
THE EXISTENCE OF THE FLEET MARINE FORCE in 1942, together with the leadership and amphibious technique it had produced, made Guadalcanal possible. This picture, taken in August 1942, shows the Marine leaders who launched the campaign, including two--Vandegrift and Cates (front row, fourth and sixth from left)--future Commandants of the Corps.
By Sundown 9 August, all ships had cleared the area, and the Marines were left with inadequate supplies, no idea as to when that condition would be ameliorated, and very meager intelligence of the enemy forces on the island. Task Force 61, whose planes had done yeoman service during the fist two days, had withdrawn, and the remnants of the cruiser force which had patrolled the western approaches to the island had been forced to leave the vicinity.
Because the force at his command was a relatively small one, General Vandegrift decided that every emphasis be placed on
defense of the Lunga point region, including the all-important airfield.1
The defense itself would be centered on the field, with the strongest positions of the perimeter placed along the beach proper as a precaution against counter-landings. This sector was organized in two regimental subsectors. Automatic weapons were sited for water's edge defense. Thirty caliber machine guns were set up so that their final protective lines would lie along the actual edge of the beach. The heavier weapons,.50 caliber machine guns and 37mm guns, were so emplaced as to be able to deliver antiboat fire. Emplacements were dug some distance back of the beach for the half-track 75mm, but the weapons themselves were kept mobile in readiness for movement forward to other prepared positions near the water's edge.2
Infantry was assigned the task of protecting these weapons emplacements and was scattered in foxholes along the line. The larger part of the force, however, was kept within the perimeter, ready to move in any direction to deal with possible penetration of the lines, as well as for counter-attacks at the proper time. Mortars in general were retained in the rear of their respective battalion positions, while the artillery, 75s and 105s of the 11th Marines, was grouped well inland to the south of the airfield in such position that it could be used for the defense of any threatened sector of the perimeter.
The entire defense area was generally in the shape of a long, flat oval with the long axis running in an east-west direction. One curve lay along the beach where there was no natural defense save the water itself. The right, or east portion, of the perimeter was bounded by Alligator Creek, a sluggish, deep stream. Such was the character of the land through which it flowed, and of the banks and the undergrowth along the, that it formed an admirable defensive position, and on e of which full advantage was to be taken in the first land action of the campaign. The left bank of this river was used as a line for the extension inland of the right flank. Machine gun emplacements were constructed at the
BEACH DEFENSES were hastily established with such meager materials as had been left by the retiring transports. Japanese counter-landing behind the Marine perimeter was a constant threat during early days of the campaign.
Map 6: The "Perimeter" -- Guadalcanal, 12 August 1942
only point where crossing seemed feasible--at the very mouth of the river, where, at low tide and during dry weather, a sand bar permitted foot passage from bank to bank along the beach.
The left or west flank of the perimeter had no such naturally advantageous terrain upon which to depend. Westward of the mouth of the Lunga, there is a re-entrant in the coast, a long sweeping concave curve toward the Matanikau River, four miles away. At a point midway between the two rivers, the grassy ridges, which are the outward boundary of the rough country of the interior, impinge suddenly upon the coastal plain, and the latter is reduced to a narrow corridor several hundred yards wide, between the beach and the hills. In this terrain, the coconut palms disappear and are replaced by lowland jungle. Passage through the region, save by the coastal road, is difficult. It was decided to anchor the left flank on this higher ground and extend the lines from the beach and across the narrowing coastal plain on