What 1968 event caused u. s. military leaders to be concerned that a quick end to the war was not possible? a. the students for a democratic society was founded. b. eugene mccarthy made a strong showing in the new hampshire primary. c. president johnson announced that he would not run for another term as president. d. the u. s. military suffered a major strategic blow in the tet offensive.

The correct answer is:
D) The US military suffered a major strategic blow in the Tet Offensive .

Explanation:
The Tet Offensive was a surprise military attack by the Vietcong (aka North Vietnamese military) on the holiday of Tet.

Tet is an important Vietnamese holiday that celebrates the Lunar New Year. This attack on several different spots previously controlled by the US and Southern Vietnamese military were destroyed or taken over by the Vietcong. This attack showed that the US that the Vietcong still had plenty of fight left in them and that this war would not be ending soon.