Jibakutai is a Japanese word that means "ground forces" or "land-based forces" in English. So, it's basically talking about the military forces that are based on the ground and not in the air or in the water.
Think of it like a game of soldiers that you might play with your friends. When you and your friends play, you might have some soldiers that are on the ground, some that are in the air, and maybe some that are in the water. In the same way, jibakutai is talking specifically about the soldiers that are on the ground.
This is really important because soldiers need to be prepared for different kinds of battles depending on where they are fighting. For example, if they are on the ground, they need to be ready to fight using different weapons and tactics than if they were in the air or in the water. So, jibakutai is all about making sure that the soldiers who are going to fight on the ground are trained and prepared in the best way possible.
Overall, jibakutai is a Japanese military term that refers to the ground forces or land-based forces that are an important part of any military operation.