Under a hail of gunfire, Serbian special forces are on the move.<br/> <br />And watching the ground assault from a safe distance are Russian and Serbian military officials.<br/> <br />The unprecedented joint military drill underscores a delicate balancing act for Serbia -- safeguard relations with its big-power ally in Russia, while pursuing closer integration with Europe.<br/> <br />It's a balancing act made all the more difficult amid rising European anger over Russian involvement in Eastern Ukraine.<br/> <br />But Serbian Defense Ministry Bratislav Gasic says the country is committed to maintaining relations with all parties.<br/> <br />(SOUNDBITE) (Serbian) SERBIAN DEFENSE MINISTER BRATISLAV GASIC SAYING:<br/> <br />"Militarily we are a neutral state, and we are devoted to four strategic pillars, which are the European Union, of course Russia, the United States and China."<br/> <br />As explosions reverberated from Russian armored personnel carriers firing 30 mm cannon and guided missiles, hundreds of soldiers advan
