The Hannibal Directive is like a rule that some countries have about what to do if their soldiers are captured in a war.
Let's imagine that a group of soldiers from one country is fighting against another country, and some of those soldiers are captured by the enemy. The Hannibal Directive says that in certain situations, the first country can take very extreme measures to try to rescue their soldiers, even if that means putting other people, like civilians, at risk.
Now, I know that might not make much sense, so let me give you an example that might help. Imagine that you and your friends are playing a game of capture the flag in your backyard. If one of your friends gets captured by the other team, you might do everything you can to rescue them, even if it means taking some risks. For example, you might sneak around to try and get behind the other team, or you might run really fast and hope you don't get tagged.
The Hannibal Directive is kind of like that game of capture the flag, but it's much more serious because it involves real soldiers and real violence. The idea behind the directive is that soldiers are supposed to do everything they can to protect each other, even if that means putting other people in danger.
Now, it's important to remember that the Hannibal Directive is very controversial, and not all countries have it. Some people feel that it's not right to put civilians at risk in order to rescue soldiers, and that doing so could actually make things worse in a war. But others argue that soldiers have a special bond with each other, and that the Hannibal Directive is necessary to protect them and ensure that they aren't left behind if they're captured.