Sentence:  The 140414 Americans who gave `` the last full measure of devotion '' to prevent disunion , preserved individual freedom in the United States from the dangers of anarchy , inherent in confederations , which throughout history have <WSD>proved</WSD> fatal in the end to all associations composed primarily of sovereign states , and to the liberties of their people . 
Meaning of the word marked with <WSD> tags:  be shown or be found to be