the increased ratio of cruiser speed, such pursuit is far more formidable than it ever was.  No expedition nowadays, however successful its evasion, can be guaranteed against naval interruption in the process of landing.  Still less can it be guaranteed against naval interference in its rear or flanks while it is securing its front against the home army.  It may seek by using large transports to reduce their number and secure higher speed, but while that will raise its chance of evasion, it will prolong the critical period of landing.  If it seek by using smaller transports to quicken disembarkation, that will decrease its chances of evasion by lowering its speed and widening the sea area it will occupy in transit.  All the modern developments in fact which make for defence in case of invasion over an uncommanded sea also go to facilitate timely contact with an expedition seeking to operate by evasion.  Nor must it be forgotten, since the problem is a combined one, that the corresponding developments ashore tell with little less force in favour of the defending army.  Such appear to be the broad principles which govern an enemy’s attempts to act with combined expeditions in our own waters, where by hypothesis we are in sufficient naval strength to deny him permanent local command.  We may now turn to the larger and more complex question of the conduct of such expeditions where the naval conditions are reversed.

By the conduct, be it remembered, we mean not only their defence but also their support, and for this reason the starting-point of our inquiry is to be found, as above indicated, in the contrast of combined expeditions with convoys.  A convoy consists of two elements—­a fleet of merchantmen and an escort.  But a combined expedition does not consist simply of an army and a squadron.  It is an organism at once more complex and more homogeneous.  Its constitution is fourfold.  There is, firstly, the army; secondly, the transports and landing flotilla—­that is, the flotilla of flat-boats and steamboats for towing them, all of which may be carried in the transports or accompany them; thirdly, the “Squadron in charge of transports,” as it came to be called, which includes the escort proper and the supporting flotilla of lighter craft for inshore work; and lastly, the “Covering squadron.”

Such at least is a combined expedition in logical analysis.  But so essentially is it a single organism, that in practice these various elements can seldom be kept sharply distinct.  They may be interwoven in the most intricate manner.  Indeed to a greater or less extent each will always have to discharge some of the functions of the others.  Thus the covering squadron may not only be indistinguishable from the escort and support, but it will often provide the greater part of the landing flotilla and even a portion of the landing force.  Similarly, the escort may also serve as transport, and provide in part not only the supporting force, but also the landing flotilla.  The fourfold constitution is therefore in a great measure theoretical.  Still its use is not merely that it serves to define the varied functions which the fleet will have to discharge.  As we proceed it will be seen to have a practical strategical value.