A major investment bank careens toward bankruptcy. It has $400 billion in assets, 85 years of history and deep ties to every major bank on Wall Street. As word of its troubles spreads, a run begins, sending its stock plummeting.

Ten years ago Wednesday, that was Bear Stearns Cos., a once-storied firm whose excessive leverage had helped put it on the brink. The Federal Reserve tried to limit the damage with extraordinary actions, first extending the firm credit before forcing it into a hasty weekend shotgun marriage to JPMorgan Chase & Co., with $29 billion in assistance.

It was the first time the Fed had intervened with a noncommercial bank since the Great Depression. “Industry participants didn’t want to see Bear Stearns go down, and they didn’t want to see others go down,” says Alan Schwartz, then Bear’s chief executive.

Today, those involved with the unprecedented Bear bailout agree it only temporarily staved off a broader meltdown. Its fall was one of the first dominoes in a downturn that months later engulfed all of Wall Street, causing stocks to shed nearly half their value, Lehman Brothers Holdings Inc. to go bankrupt, Merrill Lynch & Co. to sell itself to Bank of America Corp. for $50 billion and American International Group Inc. to take a $182 billion bailout.

The debates endure—on everything from the causes of the crisis to the government’s response. Key players in the bailout, many of whom remain in finance, have spent the last decade arguing about what was done, defending decisions made then and wondering whether it could happen again. The consensus: It would be unlikely for another big firm to get into such trouble, or for the government to orchestrate such a bailout.