During this time, there were no important military operations in Europe. The British and French declared war and blockade against Germany. Germany did likewise, beginning the Battle of the Atlantic, and German submarines destroyed many Allied ships. The Royal Air Force dropped propaganda leaflets on Germany, and Canadian troops began to arrive in Britain.
In April 1940, Germany invaded Denmark and Norway. Both sides began to fight each other again. Britain and France needed many weapons quickly and so they began to buy them from American weapon companies. The American government remained neutral but helped Britain and France by selling weapons cheaply and then by Lend-Lease of military equipment and supplies.