The following are the top stories in the Wall Street Journal. Reuters has not verified these stories and does not vouch for their accuracy. _0"> * Iraq's government girded to protect the capital from advancing insurgents, as Iranian security officials said their forces had joined the battle on Baghdad's side and the United States weighed military assistance. ( r.reuters.com/xyw99v ) * Iran has deployed Revolutionary Guard forces to fight militants that have overrun a string of Iraqi cities, and it has helped Iraqi troops win back control of most of Tikrit, Iranian security sources said. ( r.reuters.com/zyw99v ) * Alibaba Group Holding Ltd IPO-ALIB.N, responding to concerns from investors that it has been too tight-lipped, plans to give out more details about its Internet empire as it readies its potential $20 billion initial public offering. The Chinese e-commerce company, which plans to go public in the next few months, is preparing a new regulatory filing that