Simplify the following text for a Grade 11 native English-speaking person.
Original: In February 1965 , United States President Lyndon Johnson dramatically escalated the war in Vietnam by bombing North Vietnam in Operation Flaming Dart and introducing ground troops directly involved in fighting the Viet Cong in the South .
Simplified: In February 1965 , US President Lyndon Johnson made the war in Vietnam much bigger by bombing North Vietnam and putting ground troops right into fighting against the Viet Cong in the South .