On September 3rd the Allied governments declared war on Germany starting "Strange" or "Phony" war. It was called "Phony" because western allies failed to provide any meaningful support, most notably the failed to respond with an overland invasion from the West as agreed upon with Poland. Great Britain and France did however enforced a naval blockade on Germany and seized German ships.
According to the Franco-Polish military convention on the 15th day of the mobilization (that is on September 16), the French Army was to start a full scale assault on Germany.
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