What were the underlying causes of World War 1? One of the ‘’MAIN’’ underlying causes of World War 1 was militarism, alliance, imperialism, and nationalism. The assassination of archduke Ferdinand of Austria Hungary which was on June 28th, 1914 was also a big cause or a big shock of news that happened around that time he was assassinated by a Bosnian while on a good will trip to Sarajevo. The new industrialism was going to mean new advances in science warfare which included rapid-firing rifles, improved