Following his graduation from Amherst in 1954 with a BA in English, Armstrong attended Harvard University where he received a Master's degree in English Literature in 1955. In 1955 Armstrong joined the United States Army and attended the Army Language School in Monterey, California where he studied Chinese. In 1958 Armstrong received a Fullbright Scholarship and studied French and Chinese at the Institute for Advanced Languages at the Sorbonne in Paris.
It was during his stay in Paris that he met Yves Tommy-Martin (AC 1958), who was planning an automobile trip from Paris to Cape Town, South Africa. When Armstrong's Fullbright Scholarship was not renewed in 1959, he decided to join Tommy-Martin and Jean Pillu, Tommy-Martin's childhood friend. Another American, Donald Shannon, a Milwaukee native and former Air Force lieutenant, joined them not long before they left. Mindful of the dangers ahead, the four set off in specially equipped Citroen cars. Citroen, the French automaker, supplied the cars and offered a prize for the most interesting account of a trip by automobile. The four, dubbed the Franco-American Student's Automobile Tour of Africa," left France on July 4, 1959.
Following a route along the Mediterranean, they arrived in Egypt later that month. The low level of the Nile made it impossible to travel the customary ferry route and the travelers were forced to drive across they desert from Aswan, Egypt to their next stop in Wadi Halfa, Sudan. Well supplied and accompanied by the requisite guide, the party drove into the Egyptian desert expecting to be in the Republic of Sudan in two of three days. The four men never made it out of Egypt.
Having heard nothing form their son in over two months, Mrs. Catherine Armstrong contacted the U.S. State Department for help. The Egyptian Government was notified and a search was begun. Egyptian patrols found the bodies on October 26, 1959. It was estimated that the party had died sometime in early August.
There was a great deal of controversy, never officially resolved, concerning the cause of death. Official reports claimed the four died of thirst and exposure. The families found evidence that indicated the four young men were murdered.