One of the earliest and most obvious criticisms advanced against the use of railways in war was based on the vulnerability of the iron road. The destruction of a bridge, the tearing up of a few rails or the blocking of a tunnel would, it was argued, suffice to cause an interruption in the transport of troops or supplies which might be of serious consequence to the combatants prejudiced thereby, though of corresponding advantage to the other side. By means of such interruption the concentration of troops on the frontier might be delayed; an army might be divided into two or more parts, and exposed to the risk of defeat in detail; the arrival of reinforcements urgently wanted to meet a critical situation might be prevented until it was too late for them to afford the desired relief; a force advancing into an enemy's country might have its rail connection severed and be left to starve or to surrender at discretion; invaders would find that the force they were driving before them had taken the precaution to destroy their own railways as they retreated; or, alternatively, lines of railway constructed to the frontier, and depended upon to facilitate invasion of neighbouring territory, might--unless destroyed--be of material service to the enemy, should the latter become the invaders instead of the invaded. While these and other possibilities--foreshadowed more especially in the controversies which the whole subject aroused in Germany in the 'Forties--were frankly admitted, it was argued that, however vulnerable railways might be as a line of communication, it should be quite possible either to defend them successfully or to carry out on them such speedy repairs or reconstruction as would, generally speaking, permit of an early resumption of traffic; though experience was to show that these safeguards could only be assured through a well-planned and thoroughly efficient organisation prepared to meet, with the utmost dispatch and the highest degree of efficiency, all the requirements in the way of railway repairs or railway rebuilding that were likely to arise. The earliest instance of an attempt to delay the advance of an enemy by interrupting his rail communications was recorded in 1848, when the Venetians, threatened with bombardment by the Austrians, destroyed some of the arches in the railway viaduct connecting their island city with the mainland. Then in the _Italian campaign of 1859_ the allies and the Austrians both resorted to the expedient of destroying railway bridges or tearing up the railway lines; although the allies were able, in various instances, to repair so speedily the damage done by the Austrians that the lines were ready for use again by the time they were wanted.