Which past president's decisions marked significant growing presidential control over foreign affairs?

The choice of Theodore Roosevelt as the president whose decisions significantly marked the growing presidential control over foreign affairs is appropriate due to his assertive approach to both diplomacy and military intervention during his presidency (1901-1909). Roosevelt expanded the role of the executive branch in foreign policy, exemplified by his use of the "Big Stick" diplomacy, which emphasized the use of military power to achieve international goals.

One of the hallmark events during his administration was the construction of the Panama Canal, facilitated by Roosevelt's decision to support Panama's independence from Colombia. This not only displayed presidential determination in executing foreign policy initiatives but also set a precedent for future presidents to exert more direct control over foreign affairs without as much reliance on Congress.

Roosevelt also played a vital role in negotiating the end of the Russo-Japanese War, earning him a Nobel Peace Prize and further highlighting the active role of the U.S. president in international diplomacy. Through these actions, Roosevelt effectively expanded the scope and influence of presidential power in matters traditionally governed by Congress, paving the way for future presidents to take similar stances.