Many soldiers who fought in the 1861 to 1865 US Civil War suffered a life of ill health afterwards, a study says.
Abraham Lincoln was president at the time of the US Civil War
A University of California team studied 15,000 soldiers' records and found some 85% suffered physical or mental health problems, with a third having both.
The most common disorders were heart, stomach and mental health-related, the Archives of General Psychiatry said.
It was "objective" evidence of a link between war experiences and a lifetime of health problems, researchers said.
US CIVIL WAR
The US Civil War was fought from 1861 to 1865
It pitted the United States of America - the Union - against the Confederate States Of America
The confederate was a coalition of 11 pro-slavery southern states that declared their independence
The war saw over 970,000 casualties - 3% of the population - including about 560,300 deaths
In total 3m people fought
After four years of fighting, often involving hand-to-hand combat, the Union won
The US Civil War was fought between the Union and a coalition of 11 pro-slavery southern states that wanted independence.
In all, 3m people were involved, with 970,000 being injured or killed - 3% of the population.
The study said young soldiers were the most at risk, with under 17-year-olds being 93% more likely to have suffered ill-health than those aged over 31.
The researchers suggested the finding was because young soldiers were still developing emotionally and physically at the time.
And they found soldiers who were in regiments where more people were killed had a 51% increased risk of problems.
Gulf War campaign
Incidence among prisoners-of-war was also greater.
Lead researcher Professor Roxane Cohen Silver said the data from the US Civil War presented a great opportunity to assess the impacts of war.
"For the first time, we have objective records indicating that horrific war experiences are associated with a lifetime of increased physical disease and mental health difficulties.
It is hard to make comparisons with modern warfare, experts say
"Unfortunately, it's likely that the deleterious health effects seen in a war conducted more than 130 years ago are applicable to the health and well-being of soldiers fighting wars in the 21st century."
A spokeswoman for the UK's National Gulf War Veterans and Families Benevolent Association said it was hard to draw parallels between wars in the 19th Century and modern warfare.
She said: "When we discuss ill-health now, it is related to vaccines they give soldiers and chemical and biological weapons.
"Obviously, during the civil war these were not an issue. But it is true to say that the effects of war can last for many years, both physically and mentally."
Some British Gulf War veterans have long argued they have suffered from a syndrome linked to exposure to vaccinations and biological and chemical weapons.
However the Ministry of Defence stands by its position there is no proof that "Gulf War syndrome" is a "discrete pathological entity" - a specific condition with a specific cause.