What kind of defense could Iran actually mount against an attack on its nuclear and military infrastructure by Israel and/or the United States?
First of all, discount all the TV pictures of Iranian missiles being fired and troops marching in review. They are designed to boost civilian morale at home. Ironically, Western media has used them to trumpet Iran’s alleged military threat. One major US TV network, NBC, even has a fixed logo on its reports from Iran: "Iran Threat."
In reality, Iran, in spite of its 71 million population and oil wealth, is militarily quite weak. Islamic Iran has been under punishing US-led military and economic sanctions since its 1979 revolution, joining other sanctions targets North Korea and Cuba.
As a result, Iran has been unable to modernize most of its 1960’s/1970’s vintage military arsenal, much of which was supplied by the US and Britain to the Shah. Iran’s decrepit civilian aircraft fleet has also been punished by US-led embargos, resulting in numerous crashes due to worn-out equipment and lack of spare parts.