NEW YORK ( TheStreet) -- It's Aubrey McClendon versus Carl Icahn, as the investor activist makes his play for Chesapeake Energy ( CHK). On Monday, investors reacted to the news that Icahn was getting into the Chesapeake fray enthusiastically, sending Chesapeake Energy shares up to their highest price since June, on the hope that, finally, the long frustrated group who have thrown in their lot with Chesapeake's stock would see the embedded value unlocked. Icahn is now the second-largest shareholder in Chesapeake Energy, with a 5.9% stake, behind only Southeastern Asset Management, which owns more than 12% of the independent oil and gas producer's shares. Icahn was previously the 6th-largest Chesapeake shareholder, with a 2.5% stake. The heavyweights of the traditional asset management world which Icahn has now passed among the ranks of Chesapeake shareholders include The Vanguard Group, Blackrock and State Street Global Advisors. Icahn has been actively increasing his Chesapeake Energy play throughout the year, starting with a first quarter 2010 investment of more than two million shares. The gradual increase in Icahn's position in Chesapeake Energy was drowned out by Icahn's surpassing of the 5% threshold last Friday: the gloves come off at the 5% level -- or, in the least, Aubrey needs to invite Carl to a white-gloved lunch before they throw down the gloves and declare a duel for the future of the energy company. Indeed, a Chesapeake Energy spokesman said on Monday that the company looked forward to a dialogue with Icahn and they had already met on Monday for a friendly discussion. In any event, beneath the splashy headlines about the battle that pits the "controversial" and "bull-headed' CEO of one of the energy sector's biggest underperforming stocks versus the long-time activist investor, who only has money on his mind regardless of sector, there are several themes that should resonate for energy investors. From the outlook for natural gas prices in 2011, to the calculations going through the mind of Carl Icahn and the long-range, long-debated strategy of Aubrey McClendon, not even to mention the long-held Chesapeake shareholder frustration, it's all reached its culmination in Icahn's upping of his Chesapeake stock ante. Here are 2 key questions to explore as a result of the looming battle between Carl Icahn and Aubrey McClendon.