That's not a functioning way to decide if a war is likely to expand or not. Every Single War in history was "supposed to be quick". WW1 was supposed to be quick. Russia in Ukraine was supposed to be quick. Russia thought it would be a quick win, the west thought Russia would quickly collapse, and here we are...
I can tell you this is probably going to spiral out of control into a world war, and the way I know this is because everybody wants it.
Israel wants it so that Iran will be killed and the US will be forced to leave the middle east, so they can control the region.
Iran wants it so that Israel will be killed and the US will be forced to leave the middle east, so THEY can control the region.
China wants it so the US will collapse and they can control south-east Asia.
Russia wants it so the US will collapse and they can control eastern Europe.
Everybody wants this thing to spiral for a different reason, but everybody wants it to spiral...
