The Peninsular War was a big fight that happened a long time ago in Spain and Portugal.
Napoleon, who was a really powerful guy from France, wanted to take over those countries and make them part of his empire. But the people who lived there didn't like that idea and wanted to keep their independence.
So, they started fighting back against Napoleon's army, and they got some help from the British soldiers who came to fight with them.
The war lasted for a really long time, almost six years! There were lots of battles, and both sides won some and lost some. It was a very tough time for the people who lived there because there was a lot of fighting everywhere.
Finally, the British and the people of Spain and Portugal were able to defeat Napoleon's army and kick them out of their countries. This was a big victory for them because they had been fighting for so long.
The Peninsular War was a very important event in history because it showed that people can fight for their freedom and independence, and it inspired other countries to do the same.