Lyndon Johnson was the 36th President of the United States, serving from 1963 to 1969. He took office after the assassination of John F. Kennedy and is known for his ambitious domestic agenda, called the "Great Society," which aimed to eliminate poverty and racial injustice. Johnson also escalated U.S. involvement in the Vietnam War, which became a controversial aspect of his presidency. His leadership style was characterized by a strong personality and a focus on legislative achievements, including the passage of landmark civil rights laws and Medicare.