The May 22, 1964 telegram from Secretary of State Dean Rusk to Ambassador Henry Cabot Lodge in Saigon does not directly address Rusk's feelings about the South Vietnamese government's ability to fight the Communists.
However, the telegram does provide some insights into Rusk's thinking on the matter.
The telegram is in response to Lodge's query about whether the United States could launch airstrikes against North Vietnam without prior notice.
Rusk expresses his belief that such attacks would inevitably be made public, which would put the United States in a difficult position with the American people and Congress.
He also suggests that the South Vietnamese government may not be able to keep such attacks secret.
This suggests that Rusk had some concerns about the South Vietnamese government's ability to keep its own secrets, and by extension, its ability to effectively prosecute the war against the Communists.
However, it is also important to note that the telegram is primarily concerned with the potential political fallout of a surprise attack on North Vietnam, and does not necessarily reflect Rusk's overall assessment of the South Vietnamese government's capabilities.
Other sources suggest that Rusk was generally supportive of the South Vietnamese government, although he also recognized its weaknesses.
For example, in a 1963 meeting with President Kennedy, Rusk argued that the United States should continue to support South Vietnam, but that it should also pressure the South Vietnamese government to make reforms.
Overall, it is difficult to say definitively how Rusk felt about the South Vietnamese government's ability to fight the Communists. The May 22, 1964 telegram provides some insights into his thinking on the matter.