Credit Suisse replaced the head of its investment banking unit, nearly six months after the unit posted a $1 billion writedown over illiquid trades.

The Swiss bank said investment banking veteran Tim O'Hara is leaving the bank with immediate effect.

Brian Chin (pictured below), who is currently Credit Suisse's co-head of credit, will replace him and also join the bank's top management board.

Brian Chin

Credit Suisse also said that Eric Varvel, a former investment banking head who now runs the bank's asset management activities, will add a U.S. entity post to his role.

Credit Suisse Lifer

O'Hara is a Credit Suisse lifer, and has spent the last 30 years rising in the ranks of fixed income and equites, including a prominent stint leading leveraged finance loans before the financial crisis hit in 2008.

The 52-year-old American was promoted to Credit Suisse top management two years ago under former CEO and longtime associate Brady Dougan, initially as head of the equities part of investment banking.

$1 Billion Writedown

Tidjane Thiam, who took over from Dougan as CEO last July, effectively promoted O'Hara last October in a wide-ranging restructuring of the bank.

It was short-lived: O'Hara was publicly humiliated by nearly $1 billion in writedowns in illiquid trading positions earlier this year. Thiam further confused the matter by initially claiming senior bank executives hadn't been informed, which alarmed analysts. 

Email Rebuke

The bank later took the highly unconventional step of releasing correspondence between Thiam and O'Hara from early this year to newswire «Reuters» that appeared to show the CEO pressing the investment banker on the inventory of illiquid positions.

«You and I need to discuss case by case the appropriate inventory levels,» Thiam told O'Hara.

Already feeling unappreciated under the new CEO, investment bankers stepped up a very public feud with Thiam which played out in the pages of leading business papers, and led a major shareholder to remind the CEO to soften his tone.

Thiam Cements Power

On Wednesday, both Thiam and Credit Suisse chairman Urs Rohner were laudatory of O'Hara in a statement issued overnight, thanking him for his leadership, management and commitment and saying he had «excelled» in his various roles at the bank.

The closing sentence in Credit Suisse's statement was a clear assertion of power by Thiam.

 «I am confident that these management changes that I have proposed and that have been approved by the Board of Directors of Credit Suisse Group AG will drive a continued improvement in the performance of our bank,» Thiam said.