irreconcilable

adj. unwilling or unable to compromise, hostile, opposed; incompatible

n. person who is unwilling to agree; person who is unwilling to compromise

The Treaty of Versailles (1919) was a peace treaty which officially ended World War I between the Allied and Associated Powers and Germany. It was signed exactly 5 years after the assassination of Archduke Franz Ferdinand, one of the events that triggered the start of the war. Although the armistice signed on November 11, 1918 put an end to the actual fighting, it took six months of negotiations at the Paris Peace Conference to conclude a peace treaty. Of the many provisions in the treaty, one of the most important and controversial provisions required Germany and its allies to accept full responsibility for causing the war and, under the terms of articles 231-248, disarm, make substantial territorial concessions and pay reparations to certain countries that had formed the Allies. The Treaty was undermined by subsequent events starting as early as 1922 and was widely flouted by the mid thirties.
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Adjective
1. impossible to reconcile; "irreconcilable differences"
(synonym) unreconcilable
(antonym) reconcilable
(similar) hostile

adj. irreconcilableness, incompatibility

(a.)
Not reconcilable; implacable; incompatible; inconsistent; disagreeing; as, irreconcilable enemies, statements.