As the U.S. industrializes, it intensifies the foreign involvement because of the U.S. need for worldwide markets for their growing industrial and agricultural excess and the need of suppliers of raw materials for manufacturing. Many conservatives hope that oversea territories and adventures may offer an escape and safety valve for discontentment at home as they are worried about the growing violence of labor-management altercations & the trouble of farmers. Mainly, advocates of expansionist policies hope to achieve their ends by economic and diplomatic means, not by military action. Darwin’s concept of the survival of the fittest is applied not only in competition of the business world but also applies to the competition among nations. According to this theory, only the strongest will survive, and, depending on the interests of different groups, this means that the U.S. has to be strong religiously, militarily, and politically. In the international arena, the United States has to demonstrate its strength by gaining territories overseas. Expansionists spread the idea of manifest destiny so that the potential for U.S. territorial expansion applies not only to North America but to all parts of the world. Starting with the Monroe Doctrine, the United States takes a specific interest in problems of the Western Hemisphere and assume the role of guardian of Latin America, keeping them safe from European ambitions.