Final answer:
Theodore Roosevelt organized and led the Rough Riders in the Battle of San Juan during the Spanish-American War and exemplified a proactive stance in U.S. foreign policy through his 'big stick' diplomacy. He prepared the nation for involvement in global affairs by supporting allies with military resources and organizing a peacetime draft.
Step-by-step explanation:
Theodore Roosevelt's Actions During War Declarations
When war was declared, Theodore Roosevelt was an exemplar of action and leadership. Among his standout moments, during the Spanish-American War, he resigned from his Navy Department post to organize the Rough Riders and led them bravely in the Battle of San Juan. Although this information is part of Roosevelt's storied history, it is worth noting that the question may contain a mix-up with President Franklin D. Roosevelt's actions surrounding the Declaration of War after the Pearl Harbor attack in World War II.
As for Teddy Roosevelt's larger influence, he was well-known for his 'speak softly and carry a big stick' foreign policy and steered the United States more actively into world politics. This approach, coupled with his decision to aid Britain with surplus military equipment during World War II, demonstrated his understanding of the complexity of war and the need for preparedness. He also instituted a peacetime draft and traded ships for military base leases, all to strengthen U.S. military readiness.
The impact of these actions was significant; Roosevelt's leadership stimulated the country's transformation from a period of isolationism into a key player on the global stage, setting the foundations for international politics that would define the 20th century.