"the Long War". IMHO, "Долгая Война".
длительная война or затяжная война untruly, because it refers to a ONE long war. (Вот я наворотил в этой фразе)

Wiki:
The Long War, as proposed by Bobbitt, includes the First World War, the Second World War, the Korean War, the Vietnam War, as well as the Bolshevik Revolution, the Chinese Civil War, the Spanish Civil War and the Cold War.