Why did un coalition troops battle iraqi forces in 1991?

because Kuwait was invaded by Iraqi troops on August 2, 1990.

Explanation:

Kuwait was invaded by Iraqi troops on August 2, 1990. Saddam Hussein demanded control of the country's oil fields. It was the beginning of a long conflict that would lead to the Gulf War. On 6 March, the United Nations imposed an economic boycott on Iraq and two days later US President George Bush announced the deployment of troops to Saudi Arabia.

For five months, a peaceful solution was tried. Until the United States established a deadline for the withdrawal of Iraqis from Kuwait: January 15, 1991. As Saddam Hussein did not abide by the ultimatum established by George Bush, the bombing of Iraq and Kuwait began on January 17. After 40 days of intense attacks, on February 27, US President George Bush declared the victory of coalition forces. With the defeat of Iraqi troops, Saddam Hussein accepted the ceasefire proposed by the UN. More than 30,000 Kuwaitis died or were captured and about 100,000 Iraqi soldiers were killed.

d. both had been uninhabited before settlers arrived.