Nomura Holdings Inc. (NMR) said Ciaran O'Kelly has joined the firm from Bank of America Corp. (BAC) to lead the equities division in the U.S.

O'Kelly plans rapid growth, either organically or by acquisition, and intends to take on Wall Street firms on their own turf. Builders were in Nomura's New York offices over the weekend knocking down walls and moving furniture to make way for new recruits as the Japanese broker ratchets up its U.S. equities business.

"I enjoy attacking the castle rather than defending the castle ... and Nomura's going to attack the castle," said the Dublin-born O'Kelly in an interview.

Previously, O'Kelly was head of global equities at Bank of America, leading a team of more than 1,000 professionals.

Nomura has been down this road before. Japan's top brokers, including Nomura, spent hundreds of millions of dollars to become major players in the U.S. securities markets in the 1980s, but they were never able to grab more than niche roles. They are plagued by high costs, the erratic behavior of Japanese investors toward U.S. stocks, and stiff competition from U.S. firms.

"This time it's different," said O'Kelly, 41. The big U.S. money managers are keen to loosen their ties to Wall Street firms after the recent financial crisis and build deeper relationships with commercial banks and non-U.S. firms, he said. Nomura is also planning to wrest U.S. market share from Swiss bank UBS AG (UBS), which is losing clients in the wake of a U.S. tax probe.

Nomura's ramp-up in the U.S. across all asset classes is designed to fill the void in the Japanese broker's platform since it bought Lehman Brothers Holdings Inc.'s (LEHMQ) Asian and European businesses last fall.

Nomura's total U.S. headcount is now 855 people, up from about 650 in September. It has hired over 200 people in the U.S. since January, with more to come.

At a town hall meeting for the equities team in London on Tuesday, Naoki Matsuba, head of global equities at Nomura, said he would "like the U.S. equities business to replicate the scale and offer of the European equities business." There are about 730 professionals working on the London equities trading floor and around 160 in New York on equities.

The buildout will initially be supported by Nomura's European equities division, and one of O'Kelly's reporting lines will be to Rachid Bouzouba, the head of equities at Nomura International PLC. Bouzouba said growth in the U.S. will be on a "pay as you go" basis, meaning Nomura will look for results from new hires before recruiting more staff.

Nomura set a target internally in March of taking the No. 1 spot in global equities by volume within three years. It is currently No. 1 in Japan, and expects to regain the top spot in Europe this year. But in the U.S. it is a fledgling player.