Like cavalry, the military aeroplanes execute both tactical and strategical reconnaissances. Their tactical reconnaissances are carried out on shorter flights, which lead them out over the enemy trench-lines and the region immediately behind. Their object is to note any change in the clear-cut line of the trenches, as seen from above, indicative of the laying out of fresh fortifications or communication trenches; to look out for reliefs coming up; and, generally, to gauge the strength and composition of the enemy forces along a definite section of the front by noting the positions of transport columns and by locating the whereabouts of brigade and divisional headquarters. Generally the aeroplane has a specific mission, though, of course, roving flights are also made. A flight may be undertaken at the request of a battalion in the front line which has observed suspicious activity on the part of the enemy opposite, or the Intelligence may have got wind of some move which seems to require further elucidation by a peep from above. Of the same nature as these tactical reconnaissances are the flights undertaken in collaboration with the artillery, either to survey likely objectives for our guns, to locate hostile batteries that have been annoying our lines, or to perform that useful duty known as “spotting for the guns”--_i.e._, observing the effect of our artillery fire. Naturally, in the course of flights undertaken for purposes unconnected with our artillery, an aeroplane will often make observations of the greatest value to the guns. In such cases, of course, a report is immediately made to the artillery headquarters. As in these tactical reconnaissances the aeroplane is, so to speak, an extended and movable periscope for the men in the front line, so, in its strategical reconnaissance work, it may be said to serve as eyes to the General Staff. Strategical reconnaissance takes the aeroplane on longer flights far into the enemy’s country, where above towns in the war zone, about barracks and railheads and headquarters and fortifications, keen eyes may glean much that is of supreme importance to the General Staff in compiling the information as to the strength and dispositions of the enemy on which all strategy is based.