December 6, 1921: United Kingdom signs treaty recognizing independence of "Irish Free State"December 1, 1921: U.S. Navy airship C-7 demonstrates successful flight with helium rather than flammable hydrogenDecember 25, 1921: Sedition sentences, of Socialist Eugene V. Debs and 23 others, commuted by President Harding for release from prisonDecember 9, 1921: All 43 crew of U.S. Navy submarine S-48 rescued after sinking