On 1 September 1939, Germany invaded Poland under the false pretext that the Poles had carried out a series of sabotage operations against German targets.[51] Two days later, on 3 September, France and United Kingdom, followed by the fully independent Dominions[52] of the British Commonwealth[53] – Australia, Canada, New Zealand and South Africa – declared war on Germany. However, initially the alliance provided limited direct military support to Poland, consisting of a small French attack into the Saarland.[54] The Western Allies also began a naval blockade of Germany, which aimed to damage the country's economy and war effort.[55] Germany responded by ordering U-boat warfare against Allied merchant and war ships, which was to later escalate in the Battle of the Atlantic.
