The 8 Main Reasons for War

What Is a War?

A war is typically fought by a country or group of countries against an opposing country or group with the aim of achieving an objective through the use of force. Wars can also be fought within a country in the form of a civil or revolutionary war.

According to the Oxford English Dictionary, "war" is defined as

A state of armed conflict between different countries or different groups within a country.

A state of competition or hostility between different people or groups.

A sustained campaign against an undesirable situation or activity.

Wars have been a part of human history for thousands of years and have become increasingly destructive as industrialization and technology have advanced.

Why Do Wars Happen?

There is rarely one single, clear cause of conflict and, ultimately, war. The causes of a war are usually numerous and can often be intertwined in a complicated way.

Many theories have been put forth over the years as to why wars happen, and some of the greatest minds have offered their take on the subject.

In the article below, I'll provide a general overview of the eight main reasons for war. Given the many potential causes for conflict, the list does not attempt to be exhaustive but does intend to give the most common reasons.

8 Main Causes of War

Economic Gain

Territorial Gain

Religion

Nationalism

Revenge

Civil War

Revolutionary War

Defensive War

Continue reading for more information on each of these reasons for war.

1.Economic Gain

Often wars are caused by one country's wish to take control of another country's wealth. Whatever the other reasons for a war may be, there is very often an economic motive underlying most conflicts, even if the stated aim of the war is presented to the public as something more noble.

In pre-industrial times, the gains desired by a warring country might be precious materials such as gold and silver, or livestock such as cattle and horses.

In modern times, the resources that are hoped to be gained from war take the form of things like oil, minerals, or materials used in manufacturing.

Some experts believe that as the world’s population increases and basic resources become scarce, wars will be fought more often over fundamental essentials, such as water and food.

Historical examples of wars fought for economic gain

Anglo-Indian Wars (1766–1849) – The Anglo-Indian wars were a series of wars fought between the British East India Company and different Indian states. These wars led to the establishment of British colonial rule in India, which gave Britain unrestricted access to exotic and valuable resources native to the Indian continent.

Opium Wars (1839–1860) – Two wars were fought between the Qing dynasty and Western powers in the 19th century. Britain wanted to access trade with China, whereas China wished to remain independent and essentially isolated.

Japanese Invasion of Manchuria (1931–1932) – Critically short of raw materials to supply its industrial growth, Japan launched an invasion of the Chinese province of Manchuria in 1931. Following the successful conquest, the Japanese established the puppet state of Manchukuo.

2. Territorial Gain

A country might decide that it needs more land, either for living space, agricultural use, or other purposes. Territory can also be used as “buffer zones” between two hostile enemies.

Related to buffer zones are proxy wars. These are conflicts that are fought indirectly between opposing powers in a third country. Each power supports the side which best suits their logistical, military, and economic interests.

Proxy wars were particularly common during the Cold War.

Historical examples of wars fought for territorial gain

Roman Conquest of Britain (Beginning AD 43) - Motivated in part by the glory of conquest and wishing to make the Roman Empire as large as possible, the Emperor Claudius landed an invasion force on the beaches of Kent in AD43. This set off battles with the British Celtic tribes who lived on the island.

Mexican-American War (1846–1848) – This war was fought following the annexation of Texas, with Mexico claiming the land as their own. The U.S. eventually won and Texas went on to be incorporated as a state.

Serbo-Bulgarian War (1885–1886) – This was a border dispute that broke out between Bulgaria and Serbia over the territory of Eastern Rumelia.

3. Religion

Religious conflicts often have very deep roots. They can lie dormant for decades, only to re-emerge in a flash at a later date.

Religious wars can often be tied to other reasons for conflict, such as nationalism or revenge for a perceived historical slight in the past.

While different religions fighting against each other can be a cause of war, different sects within a religion (for example, Protestant and Catholic, or Sunni and Shiite) battling against one another can also instigate war.

Historical examples of wars fought for religion

The Crusades in the Holy Land (1095–1291) – These were a series of religious wars encouraged by the Latin Church during the medieval age. The aim of the crusaders was to overthrow Islamic rule and achieve Christian dominance of the region.

Greek War of Independence (1821–1829) - Fought by Greek revolutionaries against the Ottoman Empire, this war had a large religious element. This was particularly evident early on, with many Christian Greeks seeing the conflict against the Muslim Turks as a holy war.

Lebanese Civil War (1975–1990) – The Lebanese Civil War developed out of socioeconomic and political tensions, which manifested as a power conflict between the Sunni Muslim, Shiite Muslim and Christian Lebanese populations.

4. Nationalism

Nationalism in this context essentially means attempting to prove that your country is superior to another by violent subjugation. This often takes the form of an invasion.

Racism can also be linked to nationalism, as can be seen in Hitler’s Germany. Adolf Hitler went to war with Russia partly because the Russians (and eastern Europeans in general) were seen as Slavs, or a group of people who the Nazis believed to be an inferior race.

Historical examples of wars fought for nationalism

Yugoslav Wars (1991–2001) – During the breakup of Yugoslavia, various nationalist groups, such as Serbs, Croatians and Bosnians, fought each other, often fueled by historic ethnic and cultural tensions.

World War I (1914–1918) – Loyalty and patriotism drew many countries into this conflict, which was the largest conflict that the world had ever known at the time. Many Europeans believed in the cultural, economic and military supremacy of their nation and this played a major role in the war beginning and continuing.

Italo-Ethiopian War (1935–36) – Benito Mussolini rose to power in Italy on the promise that he would restore national pride to Italy. Seeking to salvage Italian prestige after a previous defeat in Ethiopia, Mussolini's troops gained full domination of the Horn of Africa in 1936.

5. Revenge

Seeking to punish, redress a grievance, or simply strike back for a perceived slight can often be a factor in the waging of war. Revenge also relates to nationalism, as the people of a country which has been wronged are motivated to fight back by pride and spirit.

Unfortunately, this can lead to an endless chain of retaliatory wars being set in motion which is very difficult to stop. Any distinction between the victim and aggressor can often become blurred, with all participants perceiving themselves as fighting a just war to right historic wrongs.

Historically, revenge has been a factor in many European wars.

Historical examples of wars fought for revenge

The Boudican Revolt – Following a failure by the Romans to honor an agreement made with her husband and the brutal rape of her daughters, Boudicca, the warrior queen of the ancient British Celtic Iceni tribe launched an all out war against the Roman occupiers. Following some initial successes by the Britons, the revolt was eventually put down.

World War II (1939–1945) – The rise of the Nazi Socialist Party and Germany's eventual domination of the European continent occurred as a result of the defeat in WWI and the subsequent Treaty of Versailles, which imposed harsh punishments on Germany.

War in Afghanistan (2001–2021) – This war could be seen as being partially motivated by revenge with the US striking back at Al Qaeda for the September 11th attacks on the World Trade Center in 2001. The terrorist group were being given safe haven by the Taliban government in Afghanistan, which prompted an American-led NATO invasion.

6. Civil War

These generally take place when there is sharp internal disagreement within a country. The disagreement can be about who rules, how the country should be run or the people's rights. These internal rifts often turn into chasms that result in violent conflict between two or more opposing groups.

Civil wars can also be sparked by separatist groups who want to form their own, independent country, or, as in the case of the American Civil War, states wanting to secede from a larger union.

Historical examples of civil wars

American Civil War (1861–1865) - The American Civil War was fought by the Union army and the Confederate army as a result of the long-standing controversy over slavery.

Russian Civil War (1917–1923) – The Russian Civil War occurred in the aftermath of the Russian Revolution, with the Red Army and the White Army vying to determine Russia's political future.

Spanish Civil War (1936–1939) – The Spanish Civil War was fought between the Republicans, who were loyal to the left-leaning Second Spanish Republic, and the Nationalists, a conservative group led by General Francisco Franco.

7. Revolutionary War

These occur when a large section of the population of a country revolts against the individual or group that rules the country because they are dissatisfied with their leadership.

Revolutions can begin for a variety of reasons, including economic hardship amongst certain sections of the population or perceived injustices committed by the ruling group. Other factors can contribute too, such as unpopular wars with other countries.

Revolutionary wars can easily descend into civil wars.

Historical examples of revolutionary wars

American Revolution (1775–1783) – The American Revolution gave the 13 North American colonies independence from British rule and established the United States of America.

French Revolution (1789–1799) – The French Revolution pitted the bourgeoisie and peasantry against the aristocracy and resulted in the end of the end of the ancien régime in France.

Haitian Revolution (1791–1804) – The Haitian Revolution was a successful slave rebellion that established Haiti as the first free black republic.

8. Defensive War

In the modern world, where military aggression is more widely questioned, countries will often argue that they are fighting in a purely defensive capacity against an aggressor, or potential aggressor, and that their war is therefore a “just” war.

These defensive wars can be especially controversial when they are launched preemptively, the argument essentially being that: “We are attacking them before they inevitably attack us.”

Historical examples of defensive wars

Gallic Wars (58 BC–50 BC) – These were fought to make the Roman Empire easier to defend. Gallic and Germanic tribes in the area had attacked Rome on a number of occasions. Invading Gaul enabled Rome to use the Rhine River as a natural defensive border.

Iraqi Conflict (2003–2011) – An international coalition led by the US invaded Iraq on the grounds that the country's leader, Saddam Hussein, was developing weapons of mass destruction and, therefore, presented a threat to surrounding countries and the rest of the world. The war was controversial as the allegations made about the weapons of mass destruction by the US and UK were shown to lack substance.

Russian Invasion of Ukraine (2022–present) – In February 2022, Russian troops invaded Ukraine in a major escalation of a conflict that had begun in 2014. Russia's leader Vladimir Putin argued that the military action was defensive in nature, with the aim being to demilitarize Ukraine, stop the further expansion of NATO, and prevent an attack on Russia. These claims have been widely disputed.