Decades after their invention, trains played a vital role in the great conflicts of the 20th century. In this first episode, Dan travels by rail to the frontlines of both the First and Second World Wars, and explores how trains were used for moving men, evacuees and supplies during the desperate struggles that engulfed Europe. Following in the footsteps of thousands of WWI British soldiers, Dan looks at how the railways helped topple Hitler by allowing the build-up of men and machines in the run up to D-Day.