The IRB formed a secret Military Council to organize the Rising. Members included Thomas Clarke, Seán Mac Diarmada, Pádraig Pearse, Joseph Plunkett, Éamon Ceannt, and Thomas McDonagh.
Funds for weapons came largely from Irish-Americans, and Sir Roger Casement also brought arms from Germany.
The Rising was planned for Easter Sunday, 23rdApril 1916. The date was chosen for its symbolic link to Christ’s sacrifice.
After the outbreak of World War I, the IRB leaders began to plan a rising, believing that "Britain’s difficulty was Ireland’s opportunity."