Not only was Vietnam's military adventurism a concern, but
during the 1960s till the 1970s, the bigger threat was Communism
supported by ideologically belligerant Russia and China.
More importantly, the bigger threat was an ambitiously ideological
China under Mao Tse Tung, with his passion for continuous
revolution.
China under his leadership had a whoppingly huge army that easily
can roll over the weaker countries of Laos, Cambodia, Thailand, and
down into Peninsular Malaysia.
The USA had feared this 'Domino Effect' from the Communist in
dominating South-east Asia, with the strategic location of
Singapore as the Main Prize.
