General Sir John French, newly appointed Lord Lieutenant of Ireland (also known as Viceroy), orders the arrest of Sinn Féin leaders based on mistaken intelligence suggesting their involvement in a pro-German plot during World War I. This event, known as the “German Plot”, leads to the arrest and internment of over 70 Sinn Féin members, including Éamon de Valera, further increasing public sympathy for the movement and radicalizing Irish nationalist opinion.