'April 10, 1915. 
L' A N D AND W A T E R, 
take full advantage of tlie assistance of liis air service only 
if he is not outranged by the artillery of the enemy, and if he 
has an adequate supply of guns and ammunition. It would 
be of no avail to him to know the exact range of the enemy's 
battery if the enemy did not allow him to place his guns 
sufficiently near enough to damage their battery, or if he had 
not sufficient ammunition for that purpose. It is thus clear 
that it is but an indirect influence which air power can exert 
when it is obtained as a result of the co-operation of air units 
with land and sea forces. An air fleet can only exert a direct 
influence if it be employed as an entirely independent force. 
The general conclusion, therefore, to be drawn from the 
facts which the writer has already explained in this, and the 
previous articles, on the Influence of Air Power is that such 
an influence can be exercised in two ways : — 
(a) Indirectly, by the co-operation of aircraft with 
cavalry, artillery, &c. 
(h) Dlrectli/, by employing aircraft as an independent 
force. 
The first demands that air fleets, or air squadrons, should 
be placed under various cavalry and artillery commanders, 
whilst the second makes it clear that they should form a forca 
capable of acting either independently or, when necessary, in 
direct co-operation with the Commander-in-Chief. The In- 
advisability of employing an air fleet, at one time indepen- 
dently, at another under the orders of cavalry or of artillery 
commanders, is obvious. Such a method would not lead to the 
close and intimate co-ordination necessary to an air fleet 
acting in co-operation with cavalry or artillery, and would 
not, on the other hand, leave the aerial force sufficiently 
free to act on its own initiative and at its own time. And 
yet to benefit fully from influence of air power it is necessary 
to be able to use its direct, as well as its indirect advantages. 
With air fleets, as we now have them, it is necessary to com- 
promise their direct, in order to profit by their indirect 
influence, and vice versd. The dilemma in which a Com- 
mander-in-Chief is at present placed as regards the employ- 
ment of the aerial force at his disposal is the following : Shall 
he employ his air fleet to exert direct influence, in which case 
he would have to forego the advantages accruing from the 
co-operation of his aircraft with his other arms, or shall ho 
employ his aerial force to exert the indirect influence with 
which we are now familiar, in which case he would have to 
renounce the possible effect of the direct influence of air 
power ? This dilemma the writer proposes to deal with in his 
next article. 
NAPOLEON'S PASSAGE of the DANUBE 
in 1809. 
By COLONEL F. N. MAUDE, C.B., late R.E. 
To show how much easier the passage of a great river 
has becotae, thanks to the improvement which 
jiaa taken place in modern armament, there is 
given here a brief account of the forcing of the 
Danube by Napoleon below Vienna. 
It was in face of the whole Austrian Army, some 240,000, 
In 1809, and there are many points of similarity between 
it and the passage of the Ehine which we shall undertake this 
year; therefore Napoleon's operation is particularly interest- 
ing at the present moment. 
In March, 1809, the Emperor had conjured out of tha 
earth, so it seemed to his enemies, one of the greatest armies 
he had ever led, consisting of about 200,000 in the first line, 
followed by many reinforcements. Its numbers came as a 
complete strategic surprise to the Austrians; but, like another 
army now arrayed against us, its magnitude had been attained 
by the sacrifice of quality, and it could no longer attack on 
the battlefield except in heavy massed formations, so curiously 
does history repeat itself. 
Essentially by weight of numbers skilfully concentrated 
at the decisive points. Napoleon had driven the Austrians 
before him right across Bavaria and through the mount.ainous 
barrier which lies between the Bavarian frontier and Vienna. 
He forced them to evacuate their capital and to transfer all 
their available troops to the left bank of the Danube, which 
runs north of the City of Vienna about thiee miles away. 
The river here is as wide as the Thames at Gravesend, 
and runs with almost equal speed — i.e., four miles an hour in 
flood, and the floods were endless that year. 
Over that width of water the artillery and musketry fir» 
of the time was of no avail, and as the Austrian pickets were 
alert on the opposite bank, which they held for thirty miles 
above the city and twenty miles below it (quite a narrow 
front even then for a quarter of a million to defend), the out- 
look for the French, the prospect of their crossing the Danube, 
was far from inspiriting. But some eight miles below Vienna 
was an island — that of Lobau, about 1,000 yards long, 300 
wide, and separated from the Austrian shore by fifty yards of 
water, its borders densely clothed by willows and reeds. 
The Emperor determined to surprise the passage of the 
river at this point. Collecting all the vessels and timber 
necessary for bridging in the little tributary which, flowing 
through Vienna, enters the Danube just above the Lobau, 
under cover of night parties of light infantry in boats cap- 
tured the island, drove out the Austrian pickets, and tho 
building of the bridge at once was begun, the while a fleet of 
boats ferried more troops to the island. The short bridges 
between Lobau and the left bank gave very little trouble to 
the French, and at daylight Napoleon attacked the villages 
of Aspern and Essliugen with the first troops to arrive on the 
ground, while ceaseless streams of reinforcements poured 
over the: bridges. 
At midday, however, a big flood poured down the river 
carrying with it quantities of timber fron^ tlie hills, breaking 
the main bridge. This was repaired again, and again 
destroyed, this time very seriously. The Austrians during 
this time, fighting with desperation, had repulsed all the 
French efforts, and, driven back, crowds of wounded and 
beaten troops came streaming into the island. 
This was, perhaps, the most critical moment ever faced 
by Napoleon. His marshals, seeing what they believed to be 
a debacle, urged instant retreat out of Lobau, using all avail- 
able boats as ferries. 
This the Emperor absolutely declined to consider. He 
realised, as perhaps his marshals did not, that at the first sign 
of withdrawal on his part all South Germany would rise 
against him, and the retreat once begun would never cease 
until the French had reached the Rhine. 
So he remained, and fortunately the next day the 
weather moderated. Then he ordered the most colossal pre- 
parations for forcing the passage of the narrow arm of the 
Danube, deploying his troops in face of a victorious army on 
the opposite side, and military history holds no like record. 
The arsenals and storehouses in Vienna supplied the 
Emperor with ample material, and after six weeks' labour 
the whole front of Lobau facing the enemy was converted into 
a huge battery of siege guns some 200 in number. These 
could sweep a zone inland 600 yards broad with such torrents 
of grape and case shot that no Austrians could survive within 
it; neither could they entrench, for the subsoil water lay too 
near the surface. 
Finally, two great bridges were completed, and a picket 
boat service was organised to deal with the fireships and rafts 
of timber which were sent by the Austrians to drift down 
the current against the bridges. 
Meanwhile they (the Austrians) had drawn as near to 
the river as the French guns would allow, and laj' literally in 
formation for immediate action confronting the French. 
In spite of this, under cover of night and later of the 
morning mists, the Emperor succeeded in sending over the 
Danube a first contingent of nearly 100,000 men, and with 
them achieved what was practically a surprise. The 100,000 
were followed before nightfall by as many more, and for forty- 
eight hours one of the greatest battles in history raged, the 
result most uncertain to either side, until at length the 
Austrians, satisfied with the punishment they had inflicted 
and knowing that great reinforcements must reach them 
before long, gave up the field to the French, and rel^ircd to a 
fiesh position, while the Imperial troops were too crippled to 
pursue. An armistice followed, and finally conditions of 
peace were arranged, with which we have nothing to do. 
What is of intei'est is for us to note how immeasurably 
simpler the case would have been for Napoleon had the 
present-day appliances, both civil and military, been avail- 
able on both sides in his time. 
13* 
