structural:scholar_edition
Modern era

Tensions in the North Sea were again heightened in 1904 by the Dogger Bank incident. During the Russo-Japanese War, several ships of the Russian Baltic Fleet, which was on its way to the Far East, mistook British fishing boats for Japanese ships and fired on them, and then upon each other, near the Dogger Bank, nearly causing Britain to enter the war on the side of Japan.

During the First World War, Great Britain's Grand Fleet and Germany's Kaiserliche Marine faced each other in the North Sea, which became the main theatre of the war for surface action. Britain's larger fleet and North Sea Mine Barrage were able to establish an effective blockade for most of the war, which restricted the Central Powers ' access to many crucial resources. Major battles included the Battle of Heligoland Bight, the Battle of the Dogger Bank, and the Battle of Jutland. World War I also brought the first extensive use of submarine warfare, and a number of submarine actions occurred in the North Sea.

The Second World War also saw action in the North Sea, though it was restricted more to aircraft reconnaissance and action by fighter/bomber aircraft, submarines and smaller vessels such as minesweepers and torpedo boats.

After the war, hundreds of thousands of tons of chemical weapons were disposed of by being dumped in the North Sea.

After the war, the North Sea lost much of its military significance because it is bordered only by NATO member-states. However, it gained significant economic importance in the 1960s as the states around the North Sea began full-scale exploitation of its oil and gas resources. The North Sea continues to be an active trade route.