On September 19, 1938 the British and French asked the Czech government to accept an agreement ceding the Sudetenland to Germany. To his credit, Czech President Eduard Benes firmly turned down this request to give up nearly half of sovereign Czech territory. Moreover, defending Czechoslovakia would be nearly impossible without the Sudetenland - further emboldening Benes to hold onto this critical piece of his nation. The well-equipped Czech army had studded the Sudetenland with a maze of fortifications embedded in rugged defensive terrain. In addition, handing over the Sudetenland would mean crippling the Czechoslovakian economy; via the loss of heavy industry and natural resources located therein. In spite of all this, the Czech cabinet refused to stand with Benes and instead voted for relinquishing the Sudetenland; ostensibly in the interest of peace. On September 21, 1938, the Czech government grudgingly gave notice of acquiescence to the German annexation of the Sudetenland.

http://www.globeatwar.com/article/september-1938-dismemberment-czechoslovakia