Just a days after the official announcement that Softbank would be acquiring Sprint Nextel, the Now Network makes an unsurprising strategic move to bolster their spectrum holdings. They bought up a 4.5 percent stake in Clearwire that was formerly owned by Eagle River. While Sprint was already a major shareholder of Clearwire, this effectively gave them a 50.8% share of the company and they moved to control the board. Here's a quote with more info,

Sprint, which already held 48 percent of Clearwire, sought the majority stake to give it added sway over the fate of the company’s wireless-networking capabilities, including lucrative airwaves needed to deliver mobile calling and data. That stands to make Sprint more attractive to Tokyo-based Softbank, which is paying $20.1 billion for most of the third-biggest U.S. mobile- phone company.

“Softbank wants firm ground in the U.S.,” said Jeff Kagan, an independent telecommunications analyst. “It gives the combined company much more spectrum, much more ability to deliver services.”

Sprint, based in Overland Park, Kansas, has no immediate plans for an outright takeover of Bellevue, Washington-based Clearwire, people with knowledge of the matter said this week. Backing by Softbank gives Sprint more firepower to use in its contest with AT&T Inc. (T) and Verizon Wireless. Still, a full Clearwire acquisition is seen as too expensive, the people said.
Originally, there was a lot of industry speculation that Sprint would not try to take control of Clearwire, because they are now "all-in" on LTE instead of WiMAX; however, the other important factor that many analysts missed was that Clearwire still holds additional spectrum, and if Sprint can control that, then it makes them even more attractive to Softbank, and will help solidify the deal.

Source: Bloomberg