His incentive at the time, he wrote in a reminiscence, was to assist the National Security Agency, which employed “vast numbers of transcribers and translators to make sense of a multitude of communication channels they monitored.” In one instance he had ARPA researchers work on using artificial intelligence to transcribe manual Morse code.

“In my view, he was one of the few people who really thought about how science and technology serve national security,” said Sharon Weinberger, author of “The Imagineers of War: The Untold Story of DARPA, the Pentagon Agency That Changed the World” (2017). “He saw the role of strategy, not just widgets or weapons to serve the Pentagon, but the bigger picture around it.”

Dr. Lukasik was an early champion of the Arpanet, which began as an experiment in computer networking. His contribution to the Arpanet, he wrote in 2014, “was helping to wrench this R&D project away from its creators, who would have liked to research it forever,” in part to promote military innovation.

Dr. Lukasik began using electronic mail in its earliest versions in 1973; indeed, he became known for running ARPA largely by email. Yet email also vexed him. Not one to throw anything away, he grew frustrated by the email piling up in his inbox.

He complained to Lawrence Roberts, who ran ARPA’s Information Processing Techniques Office. “I said, ‘Larry, this email is great, but it’s a mess!’” he recalled in an interview for “Where Wizards Stay Up Late: The Origins of the Internet” (1996). “In typical Larry fashion he came in the next day, and said, ‘Steve, I wrote some code for you.’” It was the first email management program.

Stephen Joseph Lukasik was born on March 19, 1931, in Staten Island to Stephen and Mildred (Tynan) Lukasik. His father was an accountant, his mother a bank employee.

Stephen began reading scientific literature at age 10 and at 14 knew what direction his career would take after reading newspaper accounts of the atomic bomb attacks on Japan.