Japan, a country of islands, extends along the Pacific coast of Asia. The main island is Honshu, and the country has three other large islands—Hokkaido to the north and Shikoku and Kyushu to the south. More than 4,000 smaller islands surround the four largest. A modern transportation system connects the main islands, including the Seikan Tunnel linking Honshu to Hokkaido—the world's longest railroad tunnel at 54 kilometers (33 miles). Japan's high-speed trains (known as shinkansen, or bullet trains) connect major urban areas.

About 73 percent of Japan is mountainous, and all its major cities, except the ancient capital of Kyoto, cling to narrow coastal plains. Only an estimated 18 percent of Japan's territory is suitable for settlement—so Japan's cities are large and densely populated. Tokyo, the capital, is the planet's largest urbanized area at 36 million. However, Tokyo has a worrisome environmental history of destructive earthquakes and tsunamis (seismic sea waves). A major earthquake in 1923 killed an estimated 143,000 people.

One of the most traditional and isolated societies on Earth when Commodore Matthew C. Perry sailed an American fleet into Tokyo Bay in 1853, Japan is democratic and outward-looking today. Among the top three exporters of manufactured goods, the nation has the second largest economy after that of the U.S.

Aggressive expansion across the Pacific led to war with the U.S. in 1941. Defeat ended Japan's dream of ruling Asia, and the U.S. occupation imposed a parliamentary constitution, free labor unions, and stringent land reform. Despite a lack of raw materials, the economy was revived with the help of U.S. grants, high rates of labor productivity, personal savings, and capital investment.

Emperor Hirohito's death in 1989 marked the start of an era in which Japan faces the challenges of an aging population, rising inequality of wealth, the changing role of women in society, and growing concern about security and the environment. However, Japan’s economy has been experiencing continued growth after the financial crisis of the 1990s. A global powerhouse, Japan takes its place as the world’s second largest economy.

Relations with North Korea are tense because of that country's nuclear weapons program and its abduction of Japanese citizens in the 1970s and 1980s. Japan's ties with Russia are hampered because of some small islands east of Hokkaido known as the Northern Territories—the Habomai Islands, Shikotan, Kunishiri, and Etorofu (called Iturup by Russia). Japan still claims these Russian-held islands that were taken at the end of World War II.