He attended the University of Toledo and Ohio State University, where he graduated in 1931 with a Bachelor of Science in foreign studies. Kohler studied Russian at Cornell University in 1946 and then had his first tour in Moscow from 1947-1949 working for Ambassador Walter Bedell Smith.
He entered the Foreign Service and served in Windsor (Canada), Belgrade (Yugoslavia), and Bucharest (Romania). Later they served in Athens (Greece), Cairo (Egypt), Vietnam, and Bolivia. Following a tour as Director of Voice of America, in September 1962 President John F. Kennedy named Kohler In just a few weeks the Cuban Missile Crisis began and Kohler found himself engaged in defusing a serious international crisis.
The Americans had found that the Soviets were placing nuclear missiles in Cuba.
After two weeks of tension over the risk of escalation, Nikita Khrushchev agreed to remove the missiles. The experience convinced both sides of the need for better communications.
On June 20, 1963, the two countries agreed to set up a continuous connection over a secure transatlantic cable, as a "hot line" for use in times of emergency. On August 5, 1963, the Limited Test Ban Treaty, which banned nuclear testing in the atmosphere, under water, or outer space, was signed in Moscow.
This was to be the first in a series of arms control agreements between the superpowers.
On March 6, 1967, Kohler received word that Svetlana Alliluyeva, the daughter of former Soviet leader Joseph Stalin had decided to defect to the United States. in New Delhi. He had the responsibility to inform the Soviets via their Ambassador to the United States., Anatoly Dobrynin. Kohler retired from the foreign service in 1967 with the personal rank of Career Ambassador.
The Kohlers moved to Florida and he became a professor of International Studies at the Center for Advanced International Studies of the University of Miami.
He died December 23, 1990. He and Phyllis never had children.
He was a member of the Council on Foreign Relations, Beta Gamma Sigma, Delta Upsilon, and Phi Beta Kappa.