When the First World War broke out in 1914, even though the vast majority of the socialist parties openly supported their country's war efforts, the Socialist Youth International remained steadfast in their principled opposition to war and militarism.
Ketika Perang Dunia Pertama pecah pada 1914, meski sebagian besar partai-partai sosialis secara terbuka mendukung usaha perang negaranya, Pemuda Sosialis Internasional tetap teguh pada posisinya dalam menentang perang dan militerisme.