Simplify the following text for a Grade 9 native English-speaking person.
Original: The first clash between the rival fleetsâ '' the Battle of Calabriaâ '' took place on 9 July , just four weeks after the start of hostilities .
Simplified: The first clash between the rival fleets , the Battle of Calabria , took place on 9 July 1940 , just four weeks after the start of hostilities .