EASTERN MEDITERRANEAN SEA—Britain’s newest aircraft carrier, HMS Queen Elizabeth, is helping to take on the “lion’s share” of operations against the Islamic State group in Iraq, UK naval commanders said. It has also piqued the interest of Russian warplanes, who try to keep tabs on its cutting-edge F-35 jet in a “cat-and-mouse” game with British and U.S. pilots. Speaking aboard the 65,000-ton carrier on its first-ever deployment, Commodore Steve Moorhouse said the UK is carrying out most of the missions to wipe out the remnants of the ISIS terrorist group in Iraq as the United States focuses on its withdrawal from Afghanistan. “At the moment, we’re taking on the lion’s share of that operation over Iraq, which is a fantastic, say, feather in our cap. But an achievement that ‘A,’ we’re trusted and ‘B,’ that we’re able to do that,” Moorhouse told reporters Sunday. It’s the first time that a …