Complex sentence: Cape suffered two strokes in 1954, which impaired his speech, but he fought his way back to health, and was still running the firm when he celebrated his eightieth birthday in November 1959.
Split into simpler sentences: Cape suffered two strokes in 1954, which impaired his speech, but he fought his way back to health. He was still running the firm when he celebrated his eightieth birthday in November 1959.