US Marine Corps - The Black Vault

Sauo—The Galling Defeat 375
The primary reason for the division of screening forces into two main units
and one lesser unit on the nights of 7–8 and 8–9 August was the geographical
lay of the land and the required positioning of the two transport groups to
accomplish the basic TF 62 mission.
A two-ship light cruiser unit, one Australian and one United States, was
stationed in the sector east of the meridian of Lunga ( 1600 04’E) to cover
an unlikely Japanese cruiser approach but possible enemy destroyer or PT
boat approach through the restrictive waters in and surrounding Lengo
Channel or Sealark Channel.
To the westward past Savo Island, there were two entrances to block. The
northern was 12 miles wide, the southern seven and a half miles wide. These
distances were such that the six heavy cruisers in one station keeping forma-
tion could not accomplish this blocking objective by withdrawing far enough
to the eastward of Savo Island to obtain safe night maneuvering room
without coming up against the northern Transport Area. Here it would be
highly undesirable to fight a night battle, since it would put the transports
within range of the enemy guns and torpedoes. If the heavy cruisers were
projected to the westward and immediately beyond Savo Island, having the
six heavy cruisers in one column formation at a practical night cruising speed
in limited waters, 18 knots, would open up one entrance for the enemy to
slip through when the formation was reaching the extremity of the other
entrance.
It was as simple as that.
A secondary reason for the division of the Screening Group was that Rear
Admiral Crutchley, as Commander Task Force 44, a Combined Force, during
the months prior to WATCHTOWER, had issued special instructions “cover-
ing communications, tactics, including the use of searchlights” to Task Force
44 containing both Australian and United States Ships “to cover various points
of doctrine and procedure. ” He did not issue these special instructions to
Astoria, Vincennes, or Quincy, when these United States ships and numerous
destroyers came under his temporary command off Koro Island and he became
CTG 62.6. This difference of detailed instructions influenced him, in part at
least, to think it wise to employ the Vincenne~ group, from the Combined
United States-Australian ship group “with only general direction as to coop
eration, rather than try to incorporate them within a single tactical unit.” 56
BHepburn Report, para. 92.