Relations between Portugal and Germany have been tense for some time. Portugal declared neutrality at the start of the war, but Germany leaders doubt that its neutrality is real, as the country has always been close to Britain. Portugal’s leaders meanwhile have been irritated by German’s U-boat war and by incursions German forces have made into its African colonies.
In February Portugal responded to Allied requests and interned German ships in its ports. This has angered the German government and now they declare war on the Iberian nation. The Germans believe the Portuguese army to be backward and of no great consequence; they do not expect it to make any significant contribution to the Allied war effort. Being able to invade Portuguese territory in Africa at will may even be of assistance to Lettow-Vorbeck in German East Africa; the threat of his doing so could also force the Allies to divert troops to defend Portuguese Mozambique.