A military attaché is someone who works for their country's army, but they don’t fight in wars. Instead, they go to another country and live there. Their job is to help their country's army understand what the army in the other country is like.
They also help the army in their country to make plans for any possible future wars or troubles between the two countries. Military attaches help their army understand things like the traditions, training, equipment, and strategy of the other country's army.
They also make friends with people in the other country's army, so they can work together better in the future. They might even exchange gifts or invitations to things like dinners and meetings. That way, they can learn more about each other and work better together.
Overall, military attaches help their country's army to understand and communicate better with other countries' armies, which can make a big difference in how peaceful relations are between countries.