Lately, though, the companies’ relationship has been strained. A few years ago, UPS shared some of its routing data with Amazon, according to an executive. When Amazon requested additional data, UPS—by then wary of the retailer’s intentions—refused, that executive added.

Amazon has poached more than 40 UPS supervisors, managers and executives in the last three years, according to an analysis of LinkedIn data. In September, Kniffen Kelly, a 16-year veteran working on engineering UPS’s transportation networks, left to become Amazon’s director of sort center engineering.

Cut and paste of an article from the Wall Street journal.