When Yahoo sent its letter rejecting Microsoft’s $44.6 billion bid, it ended up in the inbox of a largely unknown executive on Microsoft’s sprawling campus, Christopher P Liddell. Liddell, a former banker from New Zealand, is the behind-the-scenes architect of Microsoft’s hostile takeover bid, its first unsolicited and perhaps the most audacious attempt by a technology firm to wrestle control of a competitor. With the Yahoo board rejecting Microsoft’s advances, it will fall to Liddell, an outsider to the software industry who joined Microsoft as its CFO just two years ago, to plot the company’s next steps in this bitter battle — and in the process, reshape Microsoft’s not-invented-here culture toward making aggressive acquisitions.“You have to be disciplined and ruthless,” Liddell said by telephone before Yahoo’s board decided to rebuff the offer. “We should see acquisitions as a way of growth. We should not be embarrassed at all.”Microsoft has made acquisitions over the years, but mainly smaller ones to jumpstart a fledgling business or pick up a needed technology. Its media player, voice recognition, health search and business software, among others, are technologies Microsoft bought along with the companies that created them. However, when it has come to making big deals, it has balked until recently. Liddell, who calls himself Microsoft’s “gatekeeper of funding,” spent the weekend devising ways to raise the stakes in the fight for Yahoo, holding a series of marathon conference calls with his cadre of Wall Street advisers.More an accountant than a technologist, Liddell, who joined Microsoft after serving as CFO at International Paper, the giant forest products company, clearly has no compunction about ruffling any digital feathers. Among his alternatives is a series of bare-knuckle Wall Street tactics: First, Microsoft is planning to crisscross the US to meet with Yahoo’s largest shareholders in an election-style campaign, hoping they can put pressure on Yahoo’s board, people briefed on the company’s plans said.Microsoft could also decide to make an offer directly to shareholders, called a tender offer, which would put more pressure on Yahoo's board to negotiate. At the same time, Microsoft could also set a deadline for its bid, known as an “exploding offer”.And if Microsoft decides to make this a nasty battle, it could start a proxy contest to oust Yahoo's board at its next election; it would have until March 13 to nominate a new slate of directors.