US presidential rivals Barack Obama and John McCain have clashed sharply over Iraq, but their differences on military issues appear rooted more in temperament and style than substance, analysts say. Both candidates support a bigger US military, both say more troops are needed in Afghanistan, both would hedge against a rising China or newly resurgent Russia. "Once you get beyond the issue of America's presence in Iraq, McCain and Obama have very similar policy positions," said Loren Thompson, director of the Lexington Institute, a private research group. "Where they really differ is in their style, and in their emotions regarding national security," he said. And on the loneliest, most fateful decision a president faces -- whether to send US troops into war or combat -- the candidates are apt to be more swayed by their background, experience and personality than by any position paper.