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		1783 - The Paris Peace Treaty
		The Paris Peace Treaty formally ends the American Revolution. Some historians consider it - and not the Declaration of Independence in 1776 - the true birth of the United States of America. The treaty recognizes the USA as a sovereign nation and officially defines its borders. The US is a young nation without the military and economic clout to oust European powers from all the territory it would like to claim in North America. Leaders such as Benjamin Franklin and John Adams used diplomatic finesse to exploit the longstanding rivalry between Britain and France. Thanks in part to a British attempt to lure Americans away from an alliance with the French, Adams and Franklin win generous boundaries for the US.

		1823 - The Monroe Doctrine
		President James Monroe declares European countries are not to interfere in the Americas or attempt to re-colonize them. Such intervention, he asserts, would be "dangerous to [US] peace and safety." In return, the US would not interfere in the existing colonies or internal affairs of Europe. The doctrine represents one of the first examples of US unilateralism: James Monroe and John Quincy Adams refuse a British alliance agreement to keep the other Europeans out of the Western hemisphere. It is also unprecedented in that it proclaims an enormous amount of land as a US protectorate. Ironically, the British fleet enforces the doctrine, since the US lacks strong naval capability until the end of the 19th century.

		1898 - Spanish-American War
		The US declares war on Spain on April 25, 1898, two months after the USS Maine battleship sinks in Havana. By war's end, just eight months later, Spain loses control of its overseas empire, including Cuba, Puerto Rico, the Philippine islands, and Guam. Victory in what President Theodore Roosevelt would later dub "the splendid little war" shows the world that the US has global interests. While some Americans question what they view as imperialism, Mr. Roosevelt's "big stick" approach guides US foreign policy for years to come. In 1904, Roosevelt claims that the US is "the policeman of the Western Hemisphere," and says the US will intervene in the affairs of any nation that threatens US interests. This declaration would later be known as the "Roosevelt Corollary" of the Monroe Doctrine. In 1907, the president flexes the country's new naval muscles by sending the "Great White Fleet," 16 new battleships painted white, around the world to demonstrate the US has arrived as a major power.

		1899 - Open Door Policy
		Throughout the 19th century, Europeans and Americans covet the opening of Asia's markets. European powers crave formal control over Asian colonies, but Americans believe that formal control, or even "spheres of influence," is the wrong approach, especially toward China, seen as an enormous trade and investment opportunity. Threatened by its own weakness and European aggressiveness, the US maintains that China should remain open to all countries. In 1898, President McKinley expresses his desire for an "open door" policy with China. A year later, the US and European powers agree to respect the territorial integrity of China. The US policy of free trade would later become one of the most important principles in US diplomacy.

		1915 - Sinking of the Lusitania
		The sinking of the luxury liner Lusitania by a German U-boat on May 7, 1915 while en route from the US to England, sets the stage for the US entrance into World War I. Some 1,200 people are killed in the attack, including 128 Americans. Until then, most Americans had demanded neutrality in the intensifying European conflict. In fact, President Woodrow Wilson had pushed for a neutral stance in 1914. But the news of the Lusitania's sinking, prompted by a retaliation-minded press, helps fuel anger toward Germany and by 1917 pushes the US to join the World War.

		1920 - Defeat of Versailles Treaty
		After the horrors of World War I, President Woodrow Wilson seeks to prevent another world war by creating an international alliance called the League of Nations (the precursor to the United Nations). His principles are revolutionary because they institutionalize a new world order, and are embraced by the global community. But the US Senate defeats the treaty in 1920, symbolizing American isolationism during the 1920s and 30s. Though unilateralists strongly opposed to binding the US to the treaty's security commitments win the day, Mr. Wilson's larger ideas, about self-determination and the rule of law in international affairs, eventually become the cornerstone of global foreign policy.

		1941 - Pearl Harbor
		From the end of World War I, through the Great Depression, and into the beginning of World War II, the US withdraws from much of the rest of the world. This rise of isolationism is due in part to the sense that US participation in WWI was a failure. In addition, the complex domestic problems of the Great Depression cause the US to look inward. The US signs several neutrality acts between 1935 to 1941, preventing US involvement in international disputes. But on the morning of December 7, when Japanese airplanes attack the US naval base at Pearl Harbor, killing 2,300, Americans are thrust onto the international stage. The following day, President Roosevelt calls Dec. 7 "a date which will live in infamy," and signs a declaration of war. A day later, Germany and Italy, as partners of Japan in the Tripartite Pact, declare war on the US.

		1947 - Truman Doctrine/Marshall Plan
		The atomic bombs dropped on Hiroshima and Nagasaki in 1945 end World War II, and set off the arms race that would characterize the cold war. In 1947, President Truman, aiming to challenge Soviet ambitions, asks Congress for $400 million in aid for Greece and Turkey, a move that would become known as the Truman Doctrine. Secretary of State George C. Marshall, convinced that the poverty-stricken nations of post-World War II Europe need US support, develops a $13.3 billion plan (more than $100 billion in today's dollars) for economic revival in Western Europe, later dubbed the Marshall Plan. Both policies sought to stifle Soviet involvement in weakened countries in Europe. For the next half century, the US would commit enormous amounts of money and military power in the name of protecting its national interests and containing Soviet influence. The US would become involved in regional conflicts in Latin America, North Korea, and eventually Vietnam - making the cold war a global political, economic, and military struggle.

		1962 - Cuban Missile Crisis
		The Cuban missile crisis of October 1962 is a cold war turning point. In the fall of that year, the Soviet Union denies installing nuclear weapons in Cuba, only 90 miles from the US. But US aerial reconnaissance confirms the contrary. For two weeks in October, the world sits on edge, as President John F. Kennedy and Premier Nikita Khrushchev struggle to divert a nuclear standoff. Afterwards, both countries intensify the nuclear arms race, even as they sought to prevent the use of nuclear weapons. But while direct military confrontation between the two superpowers is averted, the US commits itself to standing firm against the spread of Soviet communism.

		1972 - Nixon's visit to China
		In 1972, the staunchly anticommunist President Richard Nixon shocks the world by becoming the first American president to visit mainland China while in office. That visit, and subsequent diplomatic meetings between high-level officials in both countries, would later be dubbed "triangular diplomacy," as the US exploits divisions between the Soviet Union and China to better its relationship with both. The visit exemplifies the Nixon-Kissinger "realpolitik": Veering from earlier notions that the US is obliged to spread its values around the globe, Mr. Nixon's administration bases its foreign policy on realist principles. Nixon believes the US should pursue its interests, restoring a balance of power among the world's major players. The perception that Nixon minimized moral considerations in foreign policy produces a backlash from the right and left in the 1970s and 1980s; both sides suggest he is abandoning American values.

		1973 - OPEC boycott
		Since the discovery of oil in Saudi Arabia in the 1930s, the relationship between the US and the Middle East has revolved around oil, along with, after World War II, the status of Israel. Ensuring access to abundant and cheap oil has topped the foreign policy agenda ever since. The catalyst for the 1973 boycott by the Organization of Petroleum Exporting Countries (OPEC) is the Yom Kippur War and US support for Israel. Saudi Arabia leads a boycott against countries supporting Israel and oil prices go through the roof. Boycotters demand a complete Israeli withdrawal from all occupied territory. The boycott causes major economic upheaval worldwide, and pushes the US to the forefront of Israeli-Arab peace negotiations. After OPEC's boycott, every US president acts compelled to take an active role in Mideast politics and policy.

		1979 - Iran Hostage Crisis
		US support for Iran's Muhammad Reza Shah Pahlevi by an Islamic revolutionary government in 1979 leads to a steady deterioration of Iran-US relations. In November, Iranian students seize the American embassy in Tehran and hold 52 people hostage for two years. Both diplomacy and a military attempt fail to release the captives. US impotence in the face of the students' demands underscores US military weakness. In fact, the US failure to resolve the crisis contributes to Ronald Reagan's victory over President Jimmy Carter in the presidential election. The hostages are released in 1981, the same day Reagan is sworn into office. The Iran hostage crisis engraves terrorism into the American public consciousness and forces US policymakers to grapple with Islamic extremism.

		1982 - Reagan's Evil Empire Speech
		President Ronald Reagan considers foreign policy a moral issue, and throughout his presidency targets the Soviet Union. By the time he steps into office, he is in a race to reclaim American power. He blames the administrations before him for allowing the Soviet threat to grow while American defense waned. He launches the largest peacetime military build-up in American history, pulls back on arms control talks with the Soviets, and pushes anticommunist guerrilla movements around the world. A centerpiece of his presidency is the Strategic Defense Initiative, dubbed Star Wars, a plan that reverses two decades of US defense policy by challenging the Soviet Union to a technological competition. Targeting the Soviet Union as the "evil empire" reshapes the world's strategic landscape. From then on, US foreign policy focuses more intently on the "evil" communist sphere that threatens US preeminence, underlining a "them against us" syndrome. This stark depiction would resurface 20 years later with President George W. Bush's "axis of evil" speech.

		1989 - Fall of Berlin Wall
		The ultimate symbol of East versus West, the Berlin Wall was constructed in 1961 at the height of cold war tensions. The wall was intended to stop the flow of people under communist rule from escaping to the more prosperous economies of the West. When it topples on November 9, 1989, citizens across the world cheer for what they believe will be the emergence of a new world order. But by the time the cold war ends with the collapse of the Soviet Union in 1991, the US has already emerged as the world's sole superpower. The new world order would be crafted largely in America's image and likeness.

		2001 - 9/11
		American economic might and global clout in the 1990s seemed uncontested. President Bill Clinton used US forces quite often in his two terms, virtually all for limited combat operations in regional conflicts. The cumulative effect of these deployments gives rise to the idea of the US as "global policeman." The stunning terrorist attacks on the Pentagon and World Trade Center on Sept. 11, 2001 shatters America's confidence in its security, bringing the US into a full-scale "war on terrorism." The Bush doctrine of targeting terrorists - and states that harbor them - leads the US into two wars, the first to end the Taliban regime in Afghanistan, the second to oust Saddam Hussein's regime in Iraq. America's aggressive new foreign policy, marked by a willingness to "go it alone," and a "you're with us, or you're with the terrorists" mentality, could signal new battles against "rogue" states and dramatic changes in long-standing alliances.