the euro against the pound, which eroded the value of Vodafone's earnings in the single-currency bloc. The company also faltered in Germany, Vodafone's largest single market in Europe, where revenue from voice service and text messaging, its traditional source of earnings, is being increasingly eroded by free Internet-based mobile calling and smartphone message applications. Revenue in Germany, where the company and T-Mobile are roughly equal as market leaders, fell 6.5 percent, to 3.9 billion. "Germany experienced a sharp slowdown in revenue momentum as well as pressure on margins," Jerry Dellis, an analyst in London at Jefferies International, a securities and investment bank, wrote in a note to clients. Huge write-downs are not unknown at Vodafone, which rose to global prominence in the late 1990s through a series of aggressive mergers and acquisitions in Europe and Asia, and the purchase of a 45 percent stake in Verizon Wireless, the largest United States wireless carrier. But the company has periodically overreached during its evolution, and economic downturns set off large accounting corrections to the value of its business. Twelve years ago, Vodafone wrote down the value of its business by the equivalent of $6.5 billion. Mr. Colao, the son of an Italian military police officer who took over as chief executive in 2008, has streamlined the company, selling stakes in operators in France, Poland, Japan, Sweden and China. In January, he was able to coax from Verizon the first dividend payment for the Verizon Wireless venture since 2005, a windfall worth 2.9