The Norwegian Shipping and Trade Mission (Nortraship) was established in London in April 1940 to administer the Norwegian merchant fleet outside German-controlled areas. Nortraship operated some 1,000 vessels and was the largest shipping company in the world.^{[citation needed]} It made a major contribution to the Allied war effort.

The British politician and Nobel Peace Prize laureate of 1959, Philip Noel-Baker commented after the war, "The first great defeat for Hitler was the battle of Britain. It was a turning point in history. If we had not had the Norwegian fleet of tankers on our side, we should not have had the aviation spirit to put our Hawker Hurricanes and our Spitfires into the sky. Without the Norwegian merchant fleet, Britain and the allies would have lost the war".

Nortraship had its main offices in London and New York City and was active during World War II. Nortraship was vital to Norway and the exile government as it lacked other means to support the Allied fight against the Axis powers. The organisation handed the various vessels back to their owners when Norway was liberated in May 1945.

In the years after World War I the Norwegian merchant fleet recouped its losses and expanded into new sectors, primarily tankers but also dry cargo vessels. The 1930s, in particular, were a growth period, in contrast to the other major shipping nations. By the end of 1938, some 7% of world tonnage was Norwegian and Norway was the fourth-largest shipping nation, behind the UK, the US and Japan. Moreover, the expansion was based on new building, thus lowering the median age of Norwegian vessels. Most of the new vessels were powered by diesel motors; they accounted for some 62% of the fleet, while Japan had some 27%, and the UK 25%. Around 42% of the fleet was modern tankers, a total of 18% of the world tanker tonnage. Norwegian shipowners were innovative and willing to take risks in ordering new vessels during the depression.

The various services needed for operation of ships had also been expanded, the most important being the classification society Det Norske Veritas but also shipbrokers, insurance companies and shipping banks. The government also played an important part in establishing and updating regulations, and in providing schools for engineers and navigators.

When Norway was invaded by Germany on 9 April 1940, the merchant fleet had been at war for seven months. Norway was neutral, but lost 58 ships and around 400 sailors. During these months much of the framework that Nortraship was to operate within was created; most importantly the Norwegian-British tonnage agreement. Called the Scheme Agreement, this stated that a percentage of the Norwegian fleet, including two thirds of the tanker tonnage, was to go on charter to Britain. In return, Norway would receive important commodities. This agreement alleviated the British problem of access to the Norwegian fleet, especially the tankers, which they regarded as of "exceptional importance".¹ To protect Norwegian neutrality, the agreement was negotiated between the British government and the Norwegian Shipowners Association.

These negotiations showed the dual nature of the Norwegian merchant fleet: it was a huge asset and also was vital to both the belligerent factions. It was necessary to tread carefully to safeguard Norwegian neutrality but to maintain the close commercial relationship with Britain. Norway's policy during World War I had been labelled that of the silent ally, and the Norwegian government wanted to continue along the same lines in World War II.

The reasons for Norway being so important for the Allies were the relative decline of the British merchant fleet, overly optimistic prewar tonnage planning and the US Neutrality Act, which effectively forbade US vessels from entering the war zone. The only other nation with a comparable merchant fleet was Netherlands, but they strongly rejected any tonnage agreement for fear of German reprisals.