Although Operation Hush never took place, considerable effort went into solving problems which would have been incurred by the tanks.
The Sea Wall
As the tanks descended to the beach, one by one, they were confronted by the biggest obstacle they were ever likely to face, the Sea Wall. This was designed to prevent the sea flooding inland and swamping the low-lying countryside behind that was typical of the region. The wall varied to some extent in different places, but at its worst it was about thirty feet high, sloping on the seaward side and with an overhanging piece at the top, rather like the crest of a breaking wave.
This the tanks, and indeed other elements of this force, had to get over before they could swing into action. To do this one male tank from each pontoon, maybe both of them, carried a short, wedge shaped ramp at the front, suspended from a beam extending from the top of the cab. Carrying this ramp the tank approached the wall until the ramp made contact with it. Then the ramp, resting on a pair of wheels, was pushed up the slope like a wheelbarrow, in front of the tank.
Since the wall was understood to be coated with green slime, and slippery, the tanks had metal segments attached to their tracks that cut through the slime and bit into the concrete wall so there was no doubt that a tank could climb, at the top the ramp was collapsed over its wheels and shoved under the protruding lip, once again sharp protrusions bit into the wall so the ramp was secure and could be detached from the tank, which was now free to climb over. This was the difficult bit, the driver had to rev the engine so that the tank lurched forwards for eighteen inches (about 45cm), catch it on the brake and repeat this performance until the tank toppled onto the top of the sea wall.
See-saws and Sledges
As this was the location of the main German defences they would already have been fired upon by the guns of the monitors, firing reduced charges, while the male tanks peeled off left and right to subdue targets further along the sea wall, or any they had missed. This was reckoned to be the crucial time. Now the female tank would climb the wall, cross the ramp and station itself at the top while a long cable, from a powerful winch attached to the starboard side of the tank, was unreeled and led down to the bottom.
Meanwhile a party of men erected a large see-saw at the top of the ramp and, one after the other, the motor vehicles and artillery would be winched up and onto the see-saw which would now level out and, because their engines were running and the drivers in place, each vehicle would be driven off the see-saw which automatically returned to its former position, ready for the next vehicle. At the same time the handcarts and motorcycle combinations would be manhandled over another nearby ramp.
Once the entire force was safely over the wall the female tank would move to a clear location from which it could winch a train of three sledges over the wall, loaded with stores. These sledges ran on parallel lengths of wire rope that ran in grooves beneath the sledge, so that they relied on friction. As they rose over the lip of the sea wall each sledge was manhandled clear of its ropes and onto wooden rollers and pushed out of the way.
Meanwhile each pair of ships, now relieved of their load but still attached to the pontoon, went astern and withdrew, although a motorised barge, loaded with reserve stores, was left high and dry on the beach. The artillery with each force consisted of four 13 pounder field guns and two 4.5 inch howitzers with their limbers. Since no horses were carried on the pontoons it is assumed that these would come with a special force, formed from elements of General Rawlinson’s Fourth Army, which came by land and was supposed to link up with the Hush force at this point.
A Problematic Plan?
A training ramp, a replica of the sea wall, was built in the dunes at Merlimont, The Tank Corps establishment on the French coast. But Colonel J. F. C. Fuller, writing after the war, said that another replica wall was built beside the public road at Teneur, where the Tank Corps did their training, and he attributes this unnecessary publicity to the failure of the scheme. Lieutenant Frank Mitchell, writing in Tank Warfare also points out that only a few German gunners, sticking to their weapons on top of the wall could have hit the tanks as they slowly rose over the top and ruined the entire plan. However the plan was eventually abandoned because the land attack from Ypres got no further than Passchendaele.
Read more about the planning of Operation Hush.
For a longer read about the controversy surrounding Passchendaele, have a look at the books below.