In the climaxing phase of World War II, then-colonel Blanchard was directed to prepare and supervise the detailed operations order for the delivery of the first atomic bomb on Hiroshima.

He was the backup pilot for the Hiroshima A-bomb drop, which was ultimately delivered by Colonel Paul W. Tibbets, Commanding Officer of the 509th Atomic Bombardment Group or Wing.

With highest priorities, crews were assembled and in March the 509th was transferred to Kwajalein, Marshall Islands, for the Bikini atomic bomb tests, that ultimately took place that July.

At the conclusion of the Crossroads tests, on August 23, 1946, then-colonel Blanchard assumed the duties of commanding officer of Roswell Army Air Field, New Mexico (renamed Walker Air Force Base in 1948), which became the permanent home of the 509th, though now again reduced to skeleton operations after the Crossroad tests.

However, in September 1946, they received orders to remain at Roswell and train and equip a very heavy bomber air force with nuclear strike capability, which became fully operational in February 1947.

Brigadier General Roger Ramey, head of the Eighth Army Air Force in Fort Worth, Texas, quickly pronounced it a misidentified weather balloon.

He was assigned the additional duty as senior Air Force member, Military Staff Committee of the United Nations, later that year.