The contribution of the airfields of North Wales to the national war effort was significant. Wales was not directly facing the hostile continent, but its long coastline was not far from neutral Eire and it presented a potential backdoor opportunity for an Axis invasion fleet. Liverpool and Machester, just to the North, were cities of huge importance and they had to be defended at all costs; the former especially once America entered the war and a colossal supply train of ships, aircraft, men and equipment moved through it. Airfields in North Wales were quickly built and developed. Some were fighter stations such as Valley and Mona on Anglesey and Llanbedr. Training in gunnery and bombing, as well as flying itself, took place at airfields such as Penrhos, Hells Mouth, Wrexham, Bodorgan and Landwrog. Hawarden, now Chester Airport, became the airfield for the huge Vickers shadow factory at Broughton which maintained the output of Wellington Bombers. Local civilians played a vital role too. In addition to their jobs at the airbases they also worked at an Ordnance factory near Wrexham and built Mulberry Harbours at Conway.