Fearing the possibility of a North Korean nuclear missile strike, Tokyo decided to prepare its residents with Cold War-era drills.

Millions of Japanese residents will participate in evacuation drills simulating a nuclear attack on Tokyo, according to the Sankei Shimbun, a Japanese newspaper. The evacuation drills will take place between January and March. It is the first time a major Japanese city has undertaken a drill of this size. Several smaller cities facing a threat from North Korea have undertaken drills where residents take shelter after hearing air raid sirens.

Japanese Prime Minister Shinzo Abe called on cities and towns to identify underground facilities that could serve as shelters in case of a missile attack.

“I believe the threat is very real and that war could break out at any time”, Ken Kato, a human rights campaigner who lives Tokyo told the Independent Tuesday. “Evacuation drills are a sensible precaution that would help to minimize casualties, in much the same way as we practice what to do in the event of a major earthquake.”

Tokyo is home to around 9.3 million people, while more than 38 million people live in its metro area. The city is dangerously close to North Korea and well within range of many of its smaller and older missiles. Last week North Korea showcased the ability to strike anywhere in the U.S. with a new intercontinental ballistic missile — a capability not needed to carry a nuclear warhead the almost 600 miles to Tokyo.

An analysis of a North Korean nuclear missile attack on Tokyo and Seoul by the US-Korea Institute at Johns Hopkins University showed that casualties from a 25 nuclear warhead attack would number anywhere from 400,000 up to 3.8 million, depending on the nuclear yield of the weapons.

This year North Korea twice hurled missiles over the northern Japanese island of Hokkaido in intermediate ballistic missile tests. North Korea also tested its most powerful nuclear device ever in September, claiming it was a thermonuclear hydrogen bomb.