Simplify the following text for a Grade 9 native English-speaking person.
Original: However , the core of Dowding 's system was implemented by Dowding himself : the use of Radio Direction Finding ( RDF , later called radar , for radio detection and ranging ) was at his behest , and its use , supplemented by information by the ROC , was crucial to the RAF 's ability to efficiently intercept incoming German aircraft .
Simplified: The core of Dowding 's system was the use of Radio Direction Finding ( RDF , later called radar , for radio detection and ranging ) .