Leonard M. Rosen, a founder of the Wachtell, Lipton, Rosen & Katz law firm, has died. He was 83.

According to Bloomberg , Rosen helped avert a New York City bankruptcy in 1975 and created a restructuring practice that would guide the U.S. through the 2008 mortgage crisis. Bloomberg said further New York City, on the verge of financial collapse, turned to Rosen, who the law firm said rallied his colleagues to work around the clock to prepare agreements, securities, legislation and tax rulings the city would need to secure financing.

More recently, with government-backed mortgage agencies Fannie Mae and Freddie Mac struggling with $5 trillion of debt they supported, the Treasury turned to the Wachtell Lipton practice he pioneered to design and implement a government rescue, Bloomberg , said.

“We will miss him greatly,” said an In Memoriam on the firm’s website. “We will be inspired by him always.”

To read the firm’s In Memoriam, click here.

To read the entire Bloomberg article, click here.