Both the German and British fleets at the start of the First World War had over a dozen dreadnought battleships each. The world was about to see the two largest navies in the world go head to head. 

But the dreadnoughts only saw action in a major battle once during World War One - at the Battle of Jutland, two years into the war. So what happened to the great naval battles of the First World War? 

How was it that the merchant ships came to play the pivotal role?