Other conditions, however, swept down upon us very quickly, and by the middle of October, after the events to be narrated in the next chapters, the trench lines on both sides reached the sea and became continuous over the whole front. Thus at the moment when the new armoured-car force was coming into effective existence at much expense and on a considerable scale, it was confronted with an obstacle and a military situation which rendered its employment practically impossible. The conclusion was forced naturally and obviously upon me, and no doubt upon others, that if the armoured car on which so much money and labour had been spent could not move _round_ the enemy’s trenches and operate against an open flank of his army, some method should be devised which would enable it to traverse and pass _over_ the trenches themselves. This subject will, however, be dealt with in its proper place. The air was the first cause that took us to Dunkirk. The armoured car was the child of the air; and the tank its grandchild. But besides all this the undefended condition of the Channel ports against any serious effort by the enemy inspired the Admiralty with lively alarm. The danger of the Germans taking Dunkirk, Calais and Boulogne stared us in the face for many anxious weeks. On September 3 I minuted to the First Sea Lord:— ‘With the Germans along the French coast, modified dispositions will become necessary. The danger from aerial attack must not be underrated. The possibility of the Germans taking very heavy guns to Calais after taking the town, and getting submarines down from the Elbe to operate from Calais as a base, should also be considered. We could of course stop any surface craft, but submarines might slip through secretly and be a great nuisance when once established. On the 10th September I went to Dunkirk myself and was to some extent reassured. I made the following note at the time for the information of those concerned:— ‘_September 11, 1914._ ‘The First Lord visited Dunkirk and Calais on the 10th instant, and conferred with the Governors of both places.