I dont think that's how silicon nitride works. I think you just need sand, coke and natural gas to catalyze nitrogen from the atmosphere. Now the rare earth metals used in the catalyzing of nitrogen from the atmosphere Im not sure about. That might come in to play since nitrates are important in production of explosives and thus probably rocket fuel. But im not sure about what elements are used here since Im not focused on it.
Yttrium- This one is important for doping ceramics.
Gadolinium-
Lanthanum-
Praseodymium-
Thorium-
Uranium- self explanatory ------------- Between dopants for alloys, catalyzing agents, cryocoolers and potential for magnets and batteries for solar powered small craft I think im just tapping on the tip of this iceberg. In all out war consuming our reserves of rare earth elements vs. China's I think we'll all be dead before we have an issue with supply.
In economic warfare it might be of strategic importance. Economic warfare could be like a cold war laying a siege before developing an advantage over your enemy to either cause him to surrender, become obvious they cannot present a threat against you or become easy enough to wage a hot war against them.