Operation Popeye was a very sneaky plan that grown-ups made a long time ago during a big war. It was a secret plan made by some people in charge of the army to make it rain more in some places where the army wanted to fight.
They did this by using some special airplanes that flew up in the sky and dropped some special materials, called chemicals, into the clouds. These chemicals made the clouds bigger and heavier, so they would rain more often than usual. This made it more difficult for the bad guys to hide or move around because there was more rain and mud on the ground.
But even though the people in charge of the army thought this plan was a good idea, it wasn't very nice for the people who lived in the places where the rain was happening more often. It could damage their homes and land, and make it harder for them to grow crops or get around.
Finally, after a while, people found out about this secret plan and they thought it wasn't very fair or good either. So they made some rules to stop people from doing it again in the future.