At the end of last year, I argued, based on the low tech kinds of weapons that we saw being used in the Iraq War, that the civil war there seemed to be largely a grass roots affair with little outside military influence.
In the past month and a half, it appears that this has changed.
There is weak evidence that anti-aircract weapons have recently started to be used against U.S. helicopters and there is weak evidence that armor piercing rounds are entering wider use. The U.S., of course, fingers Iran. But, given the drum beat of war against Iran and the U.S. record of coming up with fake intelligence to start a war, this is receiving lots of skepticism.
Suppose it is true. Does that mean that war with Iran is the right move? Not necessarily. We are already assisting in military occupations of Iraq and Afghanistan. We simply do not have the military resources to stretch a U.S. Zone of Influence from the Syrian border to the Pakistani border.
Yet, while selected air strikes or special operations missions could conceivably shut down Iran nuclear efforst that could give it nuclear bombs, since that is a highly centralized program by its very nature, nothing short of regime change and a bloody occupation far worse than the campaign in Iraq could shut down Iran's ability to ship sophisticated small arms to proxy forces in Iraq.
It is also very hard to seal the border. The U.S. is unable to do that along its comparably sized border with Mexico. Yet, on the Mexico-U.S. border, unlike the Iran-Iraq case, there is no serious allegation that the official Mexican government policy is to devote professional military forces to smuggling goods across the border.
And, efforts to control insurgent finances are useless if the weapons are being offered for free, or have access to U.S. funds going into the Shi'ite controlled ruling coalition (which may include someone who has committed terrorist acts against the U.S.).
In short, there is no good reason to believe that even if the Iranians are shipping arms to insurgent militias that U.S. military actions which is less than truly massive (something Congress would likely not authorize) could stop it.
In the same way, the U.S. ultimately backed off in both the Korean War and Vietnam War in the face of Chinese backing for local forces.