The Strategic Defence Initiative (SDI) was a proposed missile defence system intended to protect the United States and its allies from attack by ballistic strategic nuclear weapons. First publicly announced by President Ronald Reagan on March 23, 1983, the system focused on strategic defence rather than the orthodox strategic offence doctrine of mutual assured destruction (MAD).
The program was the predecessor to the current Missile Defence Agency efforts to counter limited ballistic missile attacks. Moments after being sworn in as the 45th President of the United States, the new commander-in-chief outlined his new broad plans to “Make Our Military Strong Again” via the White House official website:
“Our military needs every asset at its disposal to defend America. We cannot allow other nations to surpass our military capability,” the statement reads. “The Trump Administration will pursue the highest level of military readiness … We will also develop a state-of-the-art missile defence system to protect against missile-based attacks from states like Iran and North Korea.”