The Arab Spring has now reached the point where the anniversaries are starting to roll around. Last week marked a year since the fall of Egypt’s Hosni Mubarak. This week is the anniversary of the rather less successful revolution in Bahrain, where mass protests were crushed by the government with the assistance of Saudi troops.

Reports overnight describe a massive government effort to keep the capital quiet, but violent clashes between police and protesters have taken place in several villages. While the regime clearly has the upper hand, there seems no doubt that it retains power only by the n-ked use of force.

Following last year’s crackdown, some concessions were made: an independent commission of inquiry was appointed (which produced a highly critical report), “mistakes” were acknowledged and a range of constitutional changes were promised. But progress has been slow at best, and there is no sign that King Hamad and his circle have any intention of sharing power.

Yet the international silence on Bahrain has been striking, particularly when compared to Syria — where president Bashar al-Assad has also made periodic hollow promises of reform. But the Gulf states, including  Bahrain and Saudi Arabia, have been at the forefront first of putting pressure on Assad and now of openly supporting the Syrian opposition.

The Western reaction has been similar — anguish and condemnation with respect to Syria, silence on Bahrain.

Of course the bloodshed in Bahrain was nothing like as serious as that in Syria. But Bahrain is a small place; the estimated 63 deaths there would equate to more like a thousand in a country the size of Syria. So why the difference in response?

Part of it is religion. Bahrain has a Sunni ruling class facing protests from a mostly Shi’ite population; Syria has the opposite. The Saudi government expresses solidarity with its fellow Sunnis, but it has no such ties to Assad. Victory for the Shi’ites would be seen as a victory for Iran, the largest Shi’ite power, and Iranian influence is a powerful bogey both in the region and in the West.

But geopolitics plays a powerful role as well. Bahrain is a long-time US ally, and serves as the home of the American fifth fleet. Russia, which vetoed UN action against Syria, has its Mediterranean naval base in that country. Each great power looks after its own, pushing its ally towards compromise but unwilling to be seen to undermine them.

Of course it’s not quite that simple — it rarely is in the Middle East.

American and European concern about the violence in Syria is no doubt genuine; when protests began there it seemed as if the Americans’ first instinct was to support Assad. Great powers like stability and Assad was a classic case of “the devil you know”, but his intransigence eventually exhausted Western patience.

Russia and China, on the other hand, have not been showing up at the security council and arguing for intervention in Bahrain; their position is much closer to a principled anti-interventionism. Any precedent for assistance to rebels (as in Libya, which Russia now seems to regret having allowed) threatens to come back and bite them.

And it was the US that led the invasion of Iraq to depose a minority Sunni government and install the Shi’ite majority in power. Its failure to encourage regime change in Bahrain, despite its huge military leverage there, is just another sad case of realpolitik at work.