At a meeting on the 2nd with the prime minister, Thorvald Stauning, and the foreign minister, Peter Munch, both of them worried about the effect of war between Britain and [the Third Reich] on Denmark’s economy, he explained [Berlin’s] wish to maintain its trade with Denmark.

When the Danes reminded him of [Berlin’s] pledge under the Danish–German non‐aggression treaty of May 1939 to allow Denmark to maintain its trade with all other countries, should [the Third Reich officially] be at war, Hassell pledged that [Berlin] would allow Denmark to trade with Britain provided that Anglo‐Danish trade did not disrupt Danish–German trade.¹

Hassell and Renthe‐Fink repeated the pledge and the condition attached to it at a meeting later the same day with the director² of the foreign ministry, O.C. Mohr. When Mohr suggested that Denmark should try to arrange a three‐way agreement covering all goods and not just Danish agricultural products, as the two countries had arranged in a short‐lived agreement during the First World War, Hassell agreed; although he thought that Britain might make an agreement covering Denmark, he doubted whether similar agreements could be made with other neutral countries.³

Therefore, later that day, the foreign ministry instructed the ambassador at London, Eduard Revendow, to notify the British government confidentially that Denmark expected [the Third Reich] to abide by the terms of the non‐aggression pact.⁴

Hassell reported that the Danes were keen to keep importing from Britain.⁵ And no wonder. The Danish economy — second in the 1930s only to Iceland in its dependence on trade and even shorter of raw materials⁶ — depended on trade with Britain in particular, which provided Denmark with a healthy surplus of 300 million kroner.

In 1938, fifty‐six per cent of Danish exports had gone [to] the British Isles, mainly bacon, butter, and eggs. The sterling earned paid for cattle feeds and fertilizers, of which British middlemen, Denmark’s leading suppliers, supplied thirty‐four per cent.⁷

If war led to the disruption of Anglo‐Danish trade, Denmark might suffer a catastrophe similar to the economic collapse, from which it took years to recover, caused when Germany’s use in 1917 of unrestricted warfare led to a British blockade. [Copenhagen] had made the non‐aggression pact with [the Third Reich] in the hope of keeping up their ties with Britain.

Richard Overy in Hitler’s Scandinavian Legacy indicates another reason:

The parliamentary systems survived the economic depression of the early 1930s, unlike other European states, and during the growing international crisis from the mid‐1930s onwards the Scandinavian countries remained non‐aligned. On 27 May 1938, the four Scandinavian governments signed a declaration of neutrality to make clear their desire not to become embroiled in wider European conflicts.

They had small military forces and were not heavily armed, though Finland, bordering its powerful Soviet neighbour, was more prepared for combat than the rest. This powerlessness led the Danish government to sign an inauspicious non‐aggression pact with [the Third Reich] on 31 May 1939, but the other three states refused to enter into any specific agreements.⁴

Quoting Hanna í Horni’s British and U.S. post‐neutrality policy in the North Atlantic area 09.04.1940–1945: the role of Danish representatives, pages 43–4:

The nature of the Non‐Aggression Pact and the change it would bring to the Danish situation with regard to the other Scandinavian countries, and Britain, was played down by the Danes. It was argued that “those who tried to make out that Denmark’s co‐operation minus an active military league in the North was valueless were doing the cause of Nordic co‐operation a disservice…”³⁷ and it was also strongly pointed out that the pact did not entail any alteration to Denmark’s position as a neutral and independent state.

It was also, however, stressed by the Danish Minister of Defence that those who thought otherwise were not ‘responsible statesmen’³⁸, thus trying to undermine the critics.

[…]

Unsurprisingly the signing of the Non‐Aggression Pact also sparked off criticism abroad, especially in the Allied Press. In France the national papers Le Temps and Le Soir suggested that Denmark had signed the pact in a panic. They were also critical with regard to the fact that the act could not be construed as neutrality.⁴²

Defending their deed the Danish newspaper Social‐Demokraten, the organ of Stauning’s party, argued that “not only does the pact in no way threaten Danish exports but it even specifically guarantees that Germany in the event of war will not regard exports to a third party as an unneutral act.”⁴³

It was acknowledged that “in regard to Danish military policy it was necessary to maintain a neutrality defence also after the conclusion of the pact in order to show the world that they, like the other Scandinavian countries, would insist on their neutrality.”⁴⁴

Neville Wylie in European Neutrals and Non‐Belligerents During the Second World War, page 12:

So long as all sides refrained from contesting Berlin’s de facto political suzerainty, Denmark’s political future looked secure. Few complaints were voiced at Denmark’s non‐aggression pact with [the Third Reich] in May 1939, nor its mining of the Belts, the waters leading into the Baltic Sea, at Berlin’s behest once war began.

Danish neutrality, especially in the eyes of Foreign Minister Peter Munch, aimed not at securing Denmark’s full independence — an impossible task — but at providing the country with sufficient freedom to permit Denmark’s survival as a social, political, and cultural unit.

(Emphasis added in all cases. Needless to say, few anticommunists would even consider any of these possibilities as being behind the German–Soviet Pact of 1939 when grossly overrating its importance.)