Private equity powerhouse, The Carlyle Group, has more than 500 investment professionals across 21 countries. Of course, some of them are corporate luminaries like Louis Gerstner.

Well, after being the chairman of Carlyle since 2003, he is now departing -- his last day will be September 30th. Although, he will remain as a Senior Advisor to the firm.

Gerstner has had a stellar career. In 1993, he took the challenge of becoming IBM's (NYSE: IBM) chairman. At the time, the company was crumbling.

Despite not having much tech experience, Gerstner set forth an ambitious strategy that not only saved IBM but returned the company to greatness. He even wrote a book about his experience in a book called Who Says Elephants Can't Dance?: Leading a Great Enterprise through Dramatic Change, which is definitely worth reading.

Before his tenure at IBM, Gerstner was the CEO of RJR Nabisco, where he had to deal with the debt-load from a mega leveraged buyout (from KKR). He was also the president of American Express (NYSE: AXP) and a director of management at McKinsey & Co., Inc.

While at Carlyle, Gerstner made a big impact. He helped globalize the firm as well as diversify the investment base. As of now, Carlyle manages about $75 billion in assets across 57 funds and controls a portfolio that has aggregate revenues of $87 billion.

Tom Taulli is the author of various books, including The Complete M&A Handbook and The Edgar Online Guide to Decoding Financial Statements. He also operates MergerBook.com.