Antoine-Henri Jomini was a man who lived a long time ago and was very interested in wars and armies. He wrote books about how armies should fight and how they can win battles. He was like a teacher for army leaders who wanted to be successful in fighting wars.
Jomini said that armies should always try to attack the enemy where they are weakest and avoid fighting where they are strongest. He also believed that it was important to have good communication and a clear plan before going into battle.
Jomini's ideas were very helpful to many army leaders and they used them to win battles. Even today, his ideas are still studied by people who want to learn about military history and strategy.