One of the nation's longest and most bitter takeover battles formally ended Friday _ the last business day of the year _ with the $1.48 billion merger of Irving Bank Corp. with Bank of New York Co. Inc. The merger was approved by Irving's shareholders at a special meeting, the Bank of New York said. Bank of New York said it expected that the principal banking subsidiaries of the two holding companies, the Bank of New York and Irving Trust Co., will be merged in the first half of 1989. ``All our efforts will now be directed to forging both institutions into a major force in U.S. and worldwide banking,'' J. Carter Bacot, chairman of the merged company, said in a statement. The two banks ended a year-long feud Oct. 7, when Irving's board of directors voted to end its resistance and drop all lawsuits and anti-takeover measures. In return, Bank of New York sweetened its offer by about $200 million by slightly increasing the stock portion of its bid and adding stock warrants. The Federal Reserve Board removed the last formal obstacle to the merger Nov. 28 by approving the deal. The board originally gave conditional approval in February, extending it four times as Irving battled the takeover. The merger will nearly double Bank of New York's size, vaulting it close to the top 10 of the nation's largest banking companies. The two banks had a combined $47.8 billion in assets as of June 30. Bank of New York's bid, launched Sept. 25, 1987, was the first hostile takeover attempt among American banks.