The term "police action" is generally used to mean American military intervention in a conflict that does not follow a declaration of war by Congress. For this reason, basically every American military action since the Second World War has been a police action, though the most recent invasion of Iraq—aimed at a regime change—is not usually referred to in these terms.

The first such action was US intervention, under the auspices of the United Nations, in the Korean Conflict in 1950. Communist North Korea had invaded the South, and had nearly crushed the ruling regime before American-led UN forces invaded. The conflict, which included Chinese intervention as well, ended in a stalemate and the establishment of North and South Korea as two separate nations.

Another action was the Vietnam War, which resulted from the desire of the United States to stop the spread of communism from North Vietnam to the South. This "police action" lasted many years, and costed tens of thousands of American lives. Eventually, Vietnam was unified under communist rule.

Another incident in which the United States took on a policing role was the invasion of the small Caribbean island nation of Grenada in 1983. Grenada was ruled by a leftist leader, and President Ronald Reagan sent Marines to the island, ostensibly to protect American citizens who lived there. They ended up, however, essentially overthrowing the Grenadan government and establishing a pro-Western regime.

There are a number of examples that we could discuss where the United States took the role as an international police force. One example is in Somalia. In 1992 the United States's military set up operations in the Somali city of Mogadishu in order to protect the delivery of food aid as part of Operation Restore Hope. The following year the mission shifted partly into an attempt to end the fighting between warlords who were intercepting the food aid. Ultimately the mission failed after the deaths of 18 U.S. soldiers and the mission was abandoned in 1994.

A second example happened in the Caribbean nation of Grenada in 1983. Responding to a coup d’etat that had just occurred on the small island, the United States invaded to prevent a communist government from taking hold there. With the backing of the Organization of Eastern Caribbean States, the U.S. military took control of Grenada and re-established the former government.

One final example is the U.S. invasion of Panama in December 1989 in Operation Just Cause. Panamanian President Manuel Noriega had been supporting drug trafficking through his country as well as committing a long series of human rights abuses. In the largest American military operation since Vietnam, US forces invaded Panama with the goal of arresting Noriega and putting the democratically elected government in power. The operation was a success. It lasted five days and ended in Noreiga's surrender.

Since World War II, the United States has taken on policing roles in several situations. The first example was with the conflict in Korea. When North Korea invaded South Korea in 1950 without provocation, the United States went to the United Nations to take actions to stop this invasion. With the United States taking a leading role, the United Nations sent forces to help South Korea repel the invasion by North Korea. When the conflict ended, Korea remained divided. The United States to this day helps South Korea.

Another example of a police action was our involvement in the first Iraq war in 1990-1991. Iraq had invaded Kuwait in a border dispute. The United States along with the United Nations led the effort to remove Iraq from Kuwait. This was successfully accomplished in 1991.

A third example of a police action was when the United States along with NATO entered Serbia to keep the peace there. There was a civil war occurring between the Albanians and the Serbs in the province of Kosovo. Encouraged by the United States, NATO attacked the Serbs to stop the killing of the Albanians in the province of Kosovo.

What are examples of post-WWII incidents where America acted as a global police?

The United States military has taken a "policing" role in several conflicts since World War II. When the United States intervened in the Korean War, President Truman stated that "We are not at war" and that it was only a "police action." The reason Truman--and other presidents--have used the term "police action" to describe military conflicts is that it allows them to send U.S. troops into a conflict zone without a formal declaration of war, which would require approval from Congress. Since the Vietnam War was also never formally declared, many people refer to it as a police action, too.

The United States military has taken on more conventional policing roles, however. For instance, President Eisenhower occupied territory in Lebanon for three months during the 1958 Lebanon Crisis while the country experienced political and religious turmoil.