Jonas Salk<span> </span><span>was an American </span>medical researcher<span> and </span>virologist<span>. He discovered and developed one of the first successful </span>polio vaccines in the 1950's.
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<span>Preserving the national security of the United States, Promoting world peace, a secure global environment, and Maintaining a balance of power among nations.</span>
World War I. Main article: U-boat Campaign (World War I)
See also: Mediterranean U-boat Campaign (World War I)
<span>Submarine warfare in World War I was primarily a fight between </span>German<span> and Austro-Hungarian U-boats and Atlantic supply convoys bound for the </span>United Kingdom<span>, </span>France<span>, and </span>Russia<span>.</span>
Otto the Great established the first great kingdom after the fall of the roman empire
