The United Nations declared Expressing_publicly it to be one of the most serious incidents Catastrophe since the end of the Korean War , and by December 18 , former UN ambassador Bill Richardson said Statement tensions had escalated Expansion to become Becoming `` the most serious crisis on the Korean peninsula since the 1953 armistice , which ended Process_end the Korean War '' .

Tensions escalated Expansion and Rome declared Expressing_publicly war on Macedon .

Border skirmishes escalated Expansion following Piłsudski 's Kiev Offensive in April 1920 .