A terrain like Ukraine's, with forests, rivers, lakes, and mud everywhere, is a nightmare for invaders and a natural fortress.
On the other hand, Iran, beyond its outer mountains, consists of flat plateaus, deserts, and isolated cities—a typical land that is easy to attack but difficult to defend. This is why it has historically been invaded by foreign enemies numerous times.
In open terrain, even if defenders attempt to concentrate forces at the front to intercept, they can be easily outflanked or their rear threatened, leading to panic and quick collapse, as seen in Syria.
Moreover, 90% of Iran's oil and natural gas reserves are located in the Persian Gulf and Khuzestan. If these areas are destroyed, energy supplies will be cut off, halting both the economy and military operations.
Iran's geographical conditions make it extremely vulnerable to enemy attacks.
That's why, to deter invasion, Iran must instill fear in its enemies by demonstrating that any aggression, no matter how small, will be met with fierce retaliation.