Fall Gelb in the context of "Army Group B"

The British Expeditionary Force (BEF) was the contingent of the British Army sent to France in 1939 after Britain and France declared war on Nazi Germany on 3 September, beginning the Second World War. The BEF existed from 2 September 1939 when the BEF GHQ was formed until 31 May 1940, when GHQ closed down and its troops reverted to the command of Home Forces. During the 1930s, the British government had planned to deter war by abolishing the Ten Year Rule and rearming from the very low level of readiness of the early 1930s. The bulk of the extra money went to the Royal Navy and the Royal Air Force but plans were made to re-equip a small number of Army and Territorial Army divisions for service overseas.

General Lord Gort was appointed to the command of the BEF on 3 September 1939 and the BEF began moving to France on 4 September 1939. The BEF assembled along the Belgian–French border. The BEF took their post to the left of the French First Army under the command of the French 1st Army Group (fr:Groupe d'armées n° 1) of the North-Eastern Front (Front du Nord-est). Most of the BEF spent the Phoney War (3 September 1939 to 9 May 1940) digging field defences on the border. When the Battle of France (Fall Gelb) began on 10 May 1940, the BEF constituted 10 per cent of the Allied forces on the Western Front.

Fall Rot (Case Red) was the plan for a German military operation after the success of Fall Gelb (Case Yellow), the Battle of France, an invasion of the Benelux countries and northern France. The Allied armies had been defeated and pushed back in the north to the Channel coast, which culminated in the Dunkirk evacuation. The operation to complete the conquest of France by the German Army began on 5 June 1940. Fall Rot began with a preliminary attack over the river Somme on the Channel Coast to the Seine, beginning on 5 June and the main offensive by Army Group A on 9 June further east over the river Aisne.

World War II in the Netherlands can be broken down into 4 periods:

• September 1939 to May 1940: After the war broke out, the Netherlands declared neutrality. The country was later invaded and occupied by Germany.
• May 1940 to June 1941: An economic boom caused by orders from Germany, combined with the "velvet glove" approach from Arthur Seyss-Inquart, resulted in a comparatively mild occupation.
• June 1941 to June 1944: As the war intensified, Germany demanded higher contributions from occupied territories, resulting in a decline of living standards in the Netherlands. Repression against the Jewish population intensified and thousands were deported to extermination camps. The "velvet glove" approach ended. Meanwhile the Netherlands's East Indies possession in Asia was invaded and occupied by Japan.
• June 1944 to May 1945: Conditions in the Netherlands deteriorated further, leading to starvation and lack of fuel. The German occupation authorities gradually lost control over the situation. Nazis wanted to make a last stand and commit acts of destruction, others tried to mitigate the situation, until the country was finally liberated by the Allies. In the East Indies, Japan continued to occupy it until its surrender months later.

Despite Dutch neutrality, Nazi Germany invaded the Netherlands on 10 May 1940 as part of Fall Gelb (Case Yellow). On 15 May 1940, one day after the bombing of Rotterdam, the Dutch forces surrendered. The Dutch government and the royal family fled to London. Princess Juliana and her children sought refuge in Ottawa, Canada, until after the war.