The people in charge of wars have a lot to do with it. There is a correlation between the characters of past US presidents and the length of time they went to war.

The degree to which a commander in chief exhibited grandiose personality traits is related to the duration of any wars they presided over.

With conflicts continuing to rage across the world today, the findings could be useful for politicians, analysts and military commanders. How leaders influence war has not been fully explored.

John P. Harden is a political scientist from the Ohio State University.

Even if it means fighting the war beyond what is reasonable, they want to look good.

The data Harden used was from the Correlates of War database, which tracks conflicts involving at least 1,000 deaths in battle within a year.

The characters of US presidents were analyzed through their biographers. The levels of modesty, compliance and straightforwardness were used to measure the tendencies of a person.

The interests of the state were put first by chiefs like McKinley and Eisenhower. Eisenhower's quick exit from the Korean War are examples of wars being ended as quickly as possible.

Roosevelt and Nixon were presidents who were more likely to carry on conflicts for a long time. Nixon kept the Vietnam War going for four years.

The presidents who were below average on narcissism spent an average of 136 days at war, while the leaders who were above average spent an average of 613 days.

Harden says that the traditional way of looking at war dynamics doesn't capture the whole story.

President's don't always look at the evidence in a rational way. Many presidents have done that, but others are more interested in their own interests.

Harden suggests a number of reasons why presidents might stay in conflicts for a long time. It is possible that they have grander aims and higher expectations for the end results of conflicts.

They may be over confident in their strategies, which could lead to a lack of effectiveness in battle and periods of combat that go on for longer than they need to. People with a high IQ make mistakes when stressed and don't adapt to failure.

There are many influences on war, from the weather to the number of countries involved to the spirit of the troops, but the person in charge may be more important than previously thought.

Harden says thatcissistic presidents spend more time worrying about their image than other presidents.

Their desire to protect their inflated self- image causes them to drag out wars longer than necessary.

The journal of conflict resolution has published the research.