Is toppling the regime even possible without a full blown civil war?

You have seen what the regime is capable of doing in January. The military (IRGC+Artesh) did not defect, they stayed loyal to the regime and massacred thousands of people. They will do the same if another uprising happens. And revolution isn't possible unless the military defects or at least stays neutral. So does that mean a civil war is the only way to get rid of this regime?

And even in civil war you need some fraction of the military to defect. In Syrian civil war the Free Syrian Army was formed by some high ranked military officers who defected from the Syrian army. Within the last six months you have seen a number of video clips of Iranian soldiers claiming to defect and pledge allegiance to Reza Pahlavi, but their numbers are not known and it seems very unlikely that any high ranked officer is going to defect. So is it even possible for the revolutionaries to start a civil war let alone win it?