The Reasons

During the 1930s Adolf Hitler came to power in a politically fragmented and bankrupt Germany. During the following years it became apparent that Hitler was rebuilding Germany following the First World War and had military ambitions which made the country a threat to those about them and their allies. Most of the central European countries were catalysed (to varying degrees) by these developments and Great Britain commenced a late, but timely re-armament program.

It is fair to say that the operation to destroy the German dams in the Ruhr began on Tuesday July 26th 1938 at a meeting chaired by Air Vice Marshall W. Sholto Douglas, Assistant Chief of the Air Staff. This was a meeting of the RAF Bombing Committee and one of the main items on the agenda was to bring to the meetings attention, a potential weak point in the German industrial economy. This potential weakness was a number of reservoirs that supplied power and water to manufacturing industries which in the time of war would be turned over to war manufacture. The object of the meeting was to enquire into the extent to which effective air action against the Dams of the reservoirs until similar targets would be possible. Bombing Committee paper number 16 was circulated and this document described the types of construction and siting of the Dams along with notes on the potential damage that was caused by a number of the air dropped weapons then available. Squadron leader C G Burge representing the Air Targets Sub-Committee of Aerial Intelligence reported that the amount of water consumed in the whole of Germany was only three times that of the Ruhr and that the bulk of it was obtained from one large reservoir contained by a single large dam known as the Möhne Dam. He added that there were also four or five other reservoirs in Germany which fed the inland waterways. The destruction of which was likely to leave the waterways high and dry which would severely effect the German transportation system. It also seemed reasonable to believe that the damage caused would be extremely difficult to put right.

At this stage all discussion was about bombing the dams with existing weapons. The largest of these was then the 500lb semi-armour piercing bomb designed to be used against ships. When dropped from a sufficient height, it had penetrated in tests 5ft into concrete and the thickness of a dam at a depth of 40ft was estimated to be approximately 12ft. It was felt that if a bomb could be driven into the wall to a depth of 5ft, the remaining 7ft should be severely damaged or breached but no discussion was given to special weapons. It was recognised during the meeting that any bomb would be far more effective when placed on the wet side of the dam, rather than the dry side. The possible use of torpedoes was also discussed. The final outcome of the meeting was that at the present time it is considered that the attack should be directed primarily against the high water side of the dam. Attack against the lower side is considered less likely to be effective unless a bomb can be devised that which will develop sufficient striking velocity to achieve the necessary amount of damage at low altitude.

The seed had been sown and then matters rested for three years. In essence however the basis of Operation Chastise had been established.

1.That the destruction of the Möhne dam would remove a large percentage of the water required by the Ruhr Valley industries to produce war materials along with a substantial amount of hydro-electricity.
2.The destruction of the smaller Ruhr dams would cause some loss of electrical power and great disruption to the German inland waterway system upon which a great proportion of German industry and war making capability depended.

3.An additional fringe benefit would be the damage caused to industry and infrastructure by the release of large amounts of water from these reservoirs.