Hey there little buddy!
Imagine you're playing hide-and-seek with your friends, but instead of hiding behind trees and bushes, you dig a secret tunnel to hide in. Now, imagine that instead of playing hide-and-seek, grown-up soldiers are fighting a war and they use a similar tactic – they dig tunnels to hide in or sneak up on their enemies. That's what tunnel warfare is!
Soldiers sometimes use tunnels to move safely and secretly under the ground in a battlefield. It's like building an underground road to travel freely, without being seen or attacked. Underground tunnels can also be used to store weapons, food, or sleeping areas for soldiers.
During a war, it's not easy to pick a side. You might not know who is on your side, and who is your enemy. Tunnel warfare then becomes a really useful strategy for sneaking up on your enemies, since they would not be able to see or hear you coming. Soldiers can dig tunnels under enemy lines, pop up and attack unexpectedly, and then retreat back into the safety of their tunnels.
So, that's it in a nutshell. Think about it like playing a game where the players build secret tunnels to surprise each other. But remember, it is not a game in real life, and people can get hurt.