Simplify the following text for a Grade 6 native English-speaking person.
Original: The Georges Head battery is one of three forts in the area that were built for the purpose of defending the outer harbor . The fort became a command post in the 1890s for the coordination of all of Sydney 's harbor defences .
Simplified: The fort became the boss of all other forts in the 1890s organizing all of Sydney 's harbor forts .