What did the gulf of tonkin resolution authorized president johnson to do

 The Gulf of Tonkin resolution authorized President Johnson to deal with threats in Southeast Asia as he saw fit.

Detail:  The Gulf of Tonkin Resolution was a measure passed by US Congress that allowed the US President to make military actions, like increase troops, without formal declaration of war.  It led to huge escalation of US involvement in the Vietnam War.  The Gulf of Tonkin Resolution was passed by Congress in August, 1964, after alleged attacks on two US naval ships in the Gulf of Tonkin.  The key wording in the resolution said:

That resolution served as a blank check for President Johnson to send troops to whatever extent he deemed necessary in pursuance of the war.  Between 1964 and the end of Johnson's presidency in 1969, US troop levels in Vietnam increased from around 20,000 to over 500,000.

d. dr. francis collins