A Hired Gun for Microsoft, in Dogged Pursuit of Google

Qi Lu knows as well as anyone just how difficult it is to take on Google.

For nearly a decade, Mr. Lu played a leading role in building Yahoo's Internet search and advertising technologies. The effort was so important that Yahoo backed it with billions of dollars to acquire companies, hire armies of engineers and develop and run its own systems. Yet Yahoo fell further and further behind and many analysts said the company was simply outgunned by Google.