After seven years of trying to rebuild the iconic retailer Sears, hedge-fund manager Edward S. Lampert reversed course on Thursday, announcing that Sears Holdings Corp. will unload more than 1,200 stores in an effort to raise up to $770 million of much-needed cash.

Many on Wall Street interpreted the move as the beginning of the breakup of the company. Sears on Thursday reported a loss of more than $3 billion for 2011, and same-store sales have fallen for six straight years. The company's shares, which fell below $30 last...