[6] After his return from Vietnam, Lew became the Director of Planning and Operations (작전기획부장) under the Joint Chiefs of Staff.
While there, he met with then-President-elect Ronald Reagan's national security advisor Richard V. Allen regarding Kim Dae-jung, who was facing capital punishment on charges of sedition for his role in the Gwangju Uprising; this was the first step in a diplomatic push by Reagan that would ultimately see Kim's death sentence commuted.
[4] After his retirement, Lew continued working for the South Korean government in civilian positions.
He was named South Korea's eleventh ambassador to the United States in May 1981, succeeding Kim Yong-shik.
[11][12][13] Among other duties there, he continued to keep a close eye on Kim Dae-jung, who had gone into exile in the United States in 1982 after his prison sentence was suspended.