On this day 71 years ago, the U.S. was attacked by the Empire of Japan. At the time, U.S. President Franklin D. Roosevelt declared it a “date which will live in infamy.”

The attack shocked the nation and exposed just how unprepared and vulnerable the United States was. Today, we commemorate the soldiers and citizens who lost their lives in the attack and their families, who were left without their sons and daughters in the difficult time that followed.

The Pearl Harbor attack remains a stark reminder that conventional deterrence is not sufficient. U.S. adversaries are not always rational; after all, the Japanese generals knew that the attack would only “awaken a sleeping giant.” Yet they decided to attack anyway. The attack vividly demonstrates how important it is to be prepared to avoid another Pearl Harbor–like attack in the future.

U.S. vulnerability to a ballistic missile attack could provoke one such attack. It would take an intercontinental-range ballistic missile launched from anywhere in the world about 33 minutes to reach the U.S. homeland—and only a couple of minutes if a shorter-range missile is launched off a ship near the U.S. coast.

Sadly, the U.S. is not addressing this threat in a proper manner. Since taking office, President Obama significantly reduced the missile defense budget, scaled down the number of the Ground-Based Midcourse Defense interceptors in California and Alaska from 44 to 30, and cancelled some of the most promising developmental missile defense programs, such as the Airborne Laser, Multiple Kill Vehicle, and Kinetic Energy Interceptor.

Almost 30 years after President Ronald Reagan’s Strategic Defense Initiative speech, the U.S. remains vulnerable to a ballistic missile attack, and U.S. adversaries are ready to take advantage of this vulnerability: Iran continues its nuclear and ballistic missile programs and recently supplied the terrorist organization Hamas with hundreds of rockets to attack Israel, the U.S. only democratic ally in the Middle East. North Korea is preparing for yet another ballistic missile test, and Russia has launched the most expensive nuclear weapons modernization program since the end of the Cold War. A ballistic missile armed with a nuclear warhead could cause an electromagnetic pulse, which would damage or destroy all electronic devices in the country.

The U.S. needs a comprehensive, layered ballistic missile defense system to avoid a Pearl Harbor–like ballistic missile attack.