War is nothing new to humanity. Some wars were waged for centuries, while others have lasted only a few days or hours. Let's take a brief look at some of the longest and shortest wars in history.

The Longest Wars

Because there are disagreements on what is defined as a war, historians disagree on the starting and ending dates for many wars. Many wars were actually a series of wars, broken up by truces, or a temporary halt in hostilities. Here are two wars generally agreed to be among the longest in history.

Roman-Persian Wars (92 B.C. to 629 A.D.)

Rome was not the only great empire during its time. China was a powerful empire, but isolated to its part of the world. In direct opposition to the Roman Empire stood the Persian Empire. Starting with the old Roman Empire and the Parthian Persian Empire and ending with the Byzantine Roman Empire and the Sassanid Persian Empire, this contest lasted for 721 years. Many historians say this is the longest war in human history.

The war was basically a stand-off. Neither side had the manpower or resources to carry on extended campaigns far from their borders, so most territory conquered by one side or the other was eventually restored by re-conquest later. What this war did do, however, was weaken both empires so badly that the Arab Muslim Caliphate was able to completely take over the Sassanid Empire and drive the Roman Empire out of most of the territory in the Middle East, Egypt, and Northern Africa.

Using a looser definition of a war, some historians say the Reconquista, a period of 770 years beginning in 722, is the longest war in history.

The Hundred Years' War (1337 to 1453)

Though both sides had numerous allies, this was primarily a series of wars between the House of Plantagenet of England and the House of Valois of France over who would rule France. To cement loyalties, ruling royal families from different countries would intermarry. Edward III of England, through his French mother, was related to previous French kings. When Charles IV of France died without a direct heir, Edward III's mother, unable to claim the throne because of French law denying women that ability, claimed it for her son. The French rejected the claim, eventually resulting in war between the two countries.

The war is usually divided into three phases, with periods of truce in between. Since the early 1800s, historians have combined the entire period as the Hundred Years' War. The war was a series of ups and downs for both sides. By its conclusion, England had been driven out of France, with the exception of the port of Calais (later lost to France in 1558). French kings, for the first time since 1066, controlled almost all of France.

The war helped end feudalism in France (and to a lesser degree in England) through the rise of nationalism. Feudal armies were replaced by professional soldiers, and the knight was made obsolete by changing tactics, and technology, such as the longbow.

It was during the Hundred Years' War that Joan of Arc gained her fame by lifting the English siege at Orleans.

Technically, World War II could be considered one of the longest wars on record. Because Germany was divided after the war, it wasn't until 1990 that a re-unified Germany signed the peace treaty. By the same token, North and South Korea have never signed a peace treaty to end the Korean War, which started in 1950.

The Shortest Wars in History

It is easier for historians to agree on the shortest wars—though again, some historians differ on what should be called a war. Here are some wars that are generally said to be the shortest on record:

Anglo-Zanzibar War (August 27, 1896)

The title for shortest war goes to this one, as it only lasted 40 minutes. Without getting British permission as required by treaty, Khalid bin Barghash declared himself Sultan of Zanzibar. The British sent an ultimatum for him to step down. When he refused, the British navy bombarded his palace, setting it on fire. After 40 minutes, Khalid surrendered. The Sultan had 500 casualties, while only one British sailor was injured.

The Invasion of Anjouan (2 Days)

Comoros is an archipelago off eastern Africa in the Indian Ocean. In 2007, Mohamed Bacar refused to step down after a disputed election in Anjouan, one of the islands of Comoros. Comoros, backed by African and French allies, sent an amphibious force to Anjouan on March 24th, 2008, landing the morning of the 25th. They quickly overran the island. Bacar fled by boat, and the fighting ended.

The Football War (July 14, 1969 to July 20, 1969)

Also known as the 100-hours War, this war between El Salvador and Honduras was primarily caused by tension due to immigration issues and border disputes. During the qualifying round for the 1970 FIFA World Cup, violent rioting took place between fans of the two countries. The Salvadorian army invaded Honduras, but withdrew when a cease-fire was arranged by the Organization of American States.

Six Day War (June 5, 1967 to June 10, 1967) and the Yom Kippur War (October 6, 1973 to October 25, 1973)

Two of the shorter wars in history involved Israel and its Arab neighbors. In June of 1967, Israel made a pre-emptive strike against Egyptian forces amassing on the border between the two countries. Israel quickly defeated Egypt and its allies, and gained a great deal of territory, including the Gaza Strip, the West Bank, and the Golan Heights.

In the Yom Kippur War, Egypt and its allies, hoping to win back territory lost in the Six Day War, attacked on Israel's holiest day, completely surprising the Israelis. The attack was so sudden and surprising that Egypt, Syria, and others threatened to overrun all of Israel. Documents declassified years later indicated that Israel considered using nuclear weapons to stop the attack. Israel was able to stop the attack without using them, and launched a massive counterattack that gained back all the lost territory, plus more land along the Suez Canal.

In 1859, the U.S. and Britain had a conflict over the boundary in the Northwestern Territory, resulting in the Pig War. The "war" was triggered by the shooting of a pig, which turned out to be the only casualty. Even though troops were gathered by both sides, cooler heads prevailed, and the boundary disagreement was later settled by arbitration.