Who makes U.S. foreign policy? That question seems simple enough, and at first look the answers are also simple. But, as with most things diplomatic, the question gets more complicated when theory meets the real world.
The best place to look for the initial answer to the question is the U.S. Constitution. Drafted in 1787 as a replacement for the ineffective Articles of Confederation and adopted in 1788, the Constitution suggests the process of American diplomacy. Like most issues, however, the document does not micromanage that process.
The Federal Government
The Constitution makes very clear that the federal government, not the individual states, will conduct foreign policy. Article 1, Section 10 says, "No State shall enter into any Treaty, Alliance, or Confederation" with another nation. That's simple enough; individual U.S. states do not have sovereignty to conduct foreign policy.
The Constitution makes the president the chief foreign policy maker. Article 1, Section 2 says the president "shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, [and] other public Ministers and Consuls . . . ." Notice that the Senate is a partner in the process; more on that later.
The Founding Fathers intentionally left areas of the Constitution vague. They wanted it flexible enough to withstand the necessities of time and circumstance. That is especially true with sections dealing with the presidency. The writers of the Constitution were quite certain that George Washington would be the first president, and they trusted him to set the precedents for the office. That went for domestic as well as foreign policy making.
In the 18th and 19th Centuries, U.S. foreign policy was limited. As such, presidential worries were mostly domestic. U.S. foreign policy greatly expanded, however, in the 20th Century after the U.S fought in both world wars and took a global leadership role in 1945 after World War II. The age of atomic weapons and limited, regional wars made foreign policy and presidential decisions more complicated.
As mentioned above, the Senate serves the presidency in an "Advice and Consent" capacity. Specifically, the Senate can debate treaties that the president or his representative have crafted, and it must okay them with a two-thirds vote before they take effect. The Senate must also approve the Secretary of State and any ambassadors the president nominates.
While the Constitution does not lay out the organizational or operational rules of Congress, the Senate does have an influential Foreign Relations Committee. While the committee does not make foreign policy, its members frequently go on fact-finding and relational missions around the globe. It is also a main part of the Constitution's "advice" recommendation. The nominee for secretary of state (at this writing) -- Senator John Kerry -- was long-time chairman of that committee.
House Of Representatives
The House of Representatives also has a Committee on Foreign Affairs. While not as influential as the Senate committee, it also has the president's ear.
Article 1, Sections 7 and 8, outline other congressional powers effecting foreign policy. Any revenue-raising bill -- including those that will help pay for foreign policy initiatives -- must originate in the House. Also, both houses of Congress must approve appropriations for federal bureaus, including the State Department, all branches of the U.S. military, all U.S. embassies, and any U.S. military expedition.
Since the 1973 War Powers Act, if the president commits U.S. troops to action he must quickly give Congress his detailed rationale for doing so. If in disagreement, Congress can order him to bring those troops home in a reasonable amount of time.
Secretary of State
The Constitution does not provide for the president's cabinet, but neither does it prevent it. Washington quickly understood that the job of president was too big to handle without close administrative advisers, and he created the first cabinet. It included the first secretary of state, Thomas Jefferson. As mentioned above, however, the Senate must approve cabinet nominees.
The secretary of state does not originate foreign policy; the president does that. Rather, the secretary should echo and support the president's policies. The secretary is also expected to conduct diplomacy and find ways to implement the president's policies.
In an ideal administrative setup, the president and secretary of state should work as a team, however that has not always been the case. President Woodrow Wilson frequently ignored Secretary of State William Jennings Bryan to handle his own foreign policy; Franklin D. Roosevelt often did the same with Secretary of State Cordell Hull. Richard Nixon ignored Secretary of State William Rogers and entrusted most of the secretaries duties to National Security adviser Henry Kissinger. Barak Obama and Hillary Clinton have been an example of an effective, cooperative foreign policy team.
Military and Intelligence Agencies
U.S. military branches, the CIA, the National Security Council, and other agencies that provide information to the president or must conduct military operations (always an extreme foreign policy option) play a huge role in helping the president's administration conduct foreign policy.
The president cannot hope to make effective decisions without accurate information (which today can change minute-by-minute). He also cannot wield military power without knowing the abilities and readiness of the military branches.
While foreign policy tries to shape events, there is no doubt that events often shape foreign policy. Japanese aggression in the 1930s led the U.S. to curtail exports to Japan, which in turn led to the bombing of Pearl Harbor. The rise of the Soviet Union as a superpower after World War II led the U.S. to adopt the policy of containment. Of course, 9/11 led to the U.S.-led War on Terror.
The American Public
The American people help shape foreign policy, although their effect sometimes seems indirect. They certainly elect the president and members of Congress who must enact and approve foreign policies.
At times, however, public impact is more direct. In 1898, misled by yellow journalism, Americans widely approved going to war with Spain to oust it from Cuba. Growing outcry against the Vietnam War in the 1960s prompted President Lyndon Johnson to not seek a second full term as president and his successor, Nixon, to seek an end to the war. A Republican drubbing the in mid-term election of 2006 signaled public dissatisfaction with the Iraq War led President George W. Bush to fire his Secretary of Defense, Donald Rumsfeld, and the election of Obama in 2008 led to the end of that war in 2011.