No army can fight and no leader can govern without money, oil and electricity.
Inside his Damascus redoubt, President Bashar al-Assad might ponder the harsh truth that thousands of Syrian soldiers might still be loyal to his cause, but a shortage of these three commodities could yet crush his regime. By one well-informed estimate, Assad is running down his financial reserves so fast that he will be out of money by April at the latest.
If that moment arrives, he would confront the unedifying choice of surrendering or throwing himself entirely at the mercy of his Iranian ally.
In the past six months or so, the rebels have spread across Syria and interdicted crucial supply routes, notably the north-south highway linking Damascus with Aleppo and the route between the coast and the capital. That makes it harder for Assad to supply his forces with basic necessities, starting with fuel.
Iran might still be able to land oil at the Mediterranean port of Tartous, but getting these supplies to where they are needed becomes more difficult by the day. Syrian military bases resemble beleaguered islands surrounded by an ocean of insurgents, with their soldiers immobilised by the danger of attack and the lack of necessities.
Assad's response has been to pull back his forces to Damascus and other key cities. That makes it easier to feed and arm them, while also forcing the rebels to extend their own lines of supply and communication, which generally begin in Turkey and the northern border region.
But the price has been severe: Assad has also ceded most of rural Syria to his enemies. That gives them more opportunities to tighten the noose.
One power station complex south of Damascus supplies electricity to perhaps 8?million Syrians in the capital and the surrounding region.
If the rebels were to seize or sabotage this, what remains of the government would probably be unable to function. Already, ministries are barely working, with the phones in the foreign ministry ringing unanswered and officials quietly deserting their posts.
As the regime dies by inches before his eyes, Assad has three stark options. The first is flight to a friendly haven, probably Russia or somewhere in Latin America. Last month, his deputy foreign minister visited Cuba, Ecuador and Venezuela, perhaps preparing the ground for his exit.
But Assad has insisted that he will "live and die in Syria" and, in any case, his own entourage might depose him rather than let him go. His second option would be to battle on, perhaps gambling that his enemies might make some fantastic miscalculation.
Finally, Assad could abandon Damascus and retreat to the traditional stronghold of his Alawite sect in western Syria. This might buy his survival, but he would cease to be a president and become just another warlord in a partitioned country. And, deep down, Assad will know that his own misjudgments have left him with this excruciating choice.