It's easy to see why the Russians might support their longtime friend, who's spent billions of dollars importing Russian weapons and who provides a useful port for the Russian navy in a strategic part of the world.
It's even easier to see why Iran would stand by its only real ally in the Middle East, given that Assad has apparently been quick to share technology with the nascent nuclear nation and to provide a convenient and geographically direct path for Iranian weapons being sent to Iran's proxies, Hezbollah in Lebanon.
But what does China have to gain from standing by an international pariah in a region of the world far removed from the Far East?
China expert Gordon Chang, author of "Nuclear Showdown: North Korea Takes On The World," has a simple -- and disturbing -- explanation:
"China wants to keep Assad in power,” Chang says, “so that we do not get an opportunity to go through his archives, which will undoubtedly reveal Beijing's extensive links to the nuclear weapons programs of his country and Iran."
That's not an accusation we've heard much, and it's an explosive one, in every sense. But Chang says his reasoning is straightforward and indisputable.
"The primary backer for the Syrian program is Iran," he told me. "And the primary backer for the Iranian program is China. Remember, when Qaddafi gave up his nukes in 2003, inspectors found blueprints for one of China's warheads, complete with Chinese characters.
“If we get to go through Assad's archives, we will also see China's support for missile programs in the Middle East, especially the Iranian one. For Beijing, an opposition victory in Syria would be way worse than WikiLeaks."
But not every expert agrees that China's military technology has been quite so significant to the Syrians.
"The Chinese may have had indirect military connections with Syria, through North Korea, which as of 1992 onwards supplied Syria with Scud missiles," says University of South Carolina Professor Josef Olmert, an expert on Middle East international relations.
But, Olmert adds, "There is no evidence that China was involved in these supplies, nor for any Chinese involvement in the Syrian nuclear reactor." That reactor, of course, was destroyed by an Israeli airstrike (which Israel never formally acknowledged) in September 2007.
Olmert argues that China has more prosaic reasons for vetoing U.N. Security Council resolutions condemning Assad:
Firstly, because they can. China, he says, "saw no big damage to their overall standing in the ME by supporting Syria, as they take advantage of the fact that their economic muscle will enable them to restore any damaged relations."
And secondly, "It is important for the American audience to understand that China wants to show, not unlike Vladimir Putin and Russia, that the U.S. does not call all the shots in the international arena."
There is another reason for China's support of Assad, according to Michael Singh, managing director of the Washington Institute for Near East Policy. And it may simply be self preservation.
"China is, in general, against the idea of interfering in the political affairs of other countries, in part because it doesn't want this precedent set for its own region and for China itself," Singh said.
He said it's also not insignificant that China has a sizable Muslim population to consider. "I think China also worries about this rise of Islamic extremism or of Islamic radicals in the Middle East," he told me. "It worries, for example, about the Muslim Brotherhood, and these Salafist parties, the radical parties, which have sprung up in Egypt, and worries about what that would mean for their own Muslim population, as does Russia. And so they have been reluctant to then back a process which would bring these groups to power."
So the answer to the question, why is China supporting President Assad's murderous regime, may be threefold: weapons secrets, self preservation, and plain ego. Not an easy combination to deal with.