But lets look at what sanctions train our enemies to do:
Iran's secret weapon is its secret service. The Iranian equivalent of the CIA (the Vevak) has stayed out of politics, and been invigorated by its participation in the technology smuggling and theft efforts that have kept the Iranian armed forces viable, despite three decades of arms embargos. There's a lot of money involved, and opportunity to do side deals for non-military goods. While the Vevak agents have largely stayed away from illegal drugs, everything else has been fair game. The world wide smugglers underground is full of Iranians, and most of them belong to Vevak, or have a relationship with it.
This is similar to what happened under 1990s sanctions against Iraq and the whole ooil-for-food scam. We trained the Iraqis to establish smuggling networks to find, purchase, and bring in banned material. Without this training in the 1990s, the Baathists would have been in far worse shape to supply an insurgency after we toppled Saddam's government.
So when war is considered the last resort and the argument is that we should give sanctions a chance, remember that if the sanctions don't work to topple the regime, all we will have done is make the enemy more effective at resisting us when we take that last resort option.