Russian ships have been sending massive quantities of Iranian-made artillery shells and ammunition across the Caspian Sea to help resupply Russian troops fighting in Ukraine.

The supply pipeline is causing problems for the US and allies who are trying to disrupt the cooperation happening between Tehran and Moscow.

Officials and documents informed The Wall Street Journal recently that cargo ships have now transported over 300k artillery shells and 1 million rounds of ammunition from Iran to Russia in just the past six months.

According to US officials, Iran uses mostly cargo ships to send the supplies to Russia, making it nearly impossible to intervene. And they would need help from former Soviet republics on the coast of the Caspian Sea to take any action.

It does not seem, however, that Iran has sent ballistic missiles to Russia – yet. One positive among the bad news that keeps trickling in.

Anna Borshchevskaya, a senior fellow at the Washington Institute for Near East Policy, says that Iran’s relationship with Russia is moving from transactional to strategic, and it’s no mistake. “Russia is now dependent on Iran for the first time int he broad scope of the Russia-Iran relationship. It’s a historic shift.”