Japan is deploying around 23,000 police officers to secure the Group of Seven (G7) summit being held in the tourism region of Ise-Shima.
And the navy is posting a destroyer offshore near the island hotel venue where the G7 leaders are meeting on Thursday and Friday.
There will also be around 100 smaller vessels operated by the Coast Guard. In addition, 5,000 police will be on hand to protect US President Barack Obama's subsequent visit to Hiroshima on Friday.
The security deployment is the largest in decades, in a country that is regarded as one of the safest in the world.
Japan is unaccustomed to headlines about the use of teargas and police batons, which in Western countries are often associated with G7 summits. There is no tradition of a political counterculture prepared to resort to violence.
Nevertheless, the government is leaving nothing to chance. Security is tight in Tokyo, with 19,000 police mobilized, even though the capital is 300 kilometres away from the G7 venue.
East Japan Railway is planning to seal its rubbish bins on high-speed trains and on station platforms.
In Mie Prefecture where the summit venue is located, schools have been closed in response to traffic restrictions.
Visitors to Chubu International Airport are undergoing security checks before they even enter the terminal, and the viewing platform has been closed.