The military campaign in Libya began with what seemed a narrowly defined mission: To enforce a no-fly zone and protect civilians from attack. Two months later, the campaign has evolved into a ferocious pounding of the country’s capital, Tripoli, in what appears an all-out effort to oust Colonel Muammar Gaddafi. But that goal remains elusive, raising the prospect of a quagmire in the desert. And the political will of the countries involved is being sorely tested.