The Northeast passage is a shipping route from Europe passing north of the European continent, north of Russia to Asia and back. Sailing trough the Arctic Ocean
As early as 1525 people have tried to sail from Europe to Asia via the Northern Ice Sea. In 1878-79 The first ship managed to sail the whole route. But it would take until 1932 before a ship could pass in one season (without freezing in the ice over winter and surviving till next spring).
The Northeast passage is only completely free of (solid sheet) ice from July to October, the other months ships have to plow through ice, a lot of times with the assistance of (nuclear powered) icebreakers.
Using the Northeast passage saves 10-40% on the distance depending on the ports compared to the route via the Suez-canal. Saving a lot on time and fuel.
The Royal Netherlands Navy ship Zr.Ms. Willem Barentsz was the first non Russian warship to sail the Northeast passage. They passed together with a flotilla of Russian warships to celebrate the newly formed alliance between Russia and the Netherlands.