Gallium and germanium are used in lots of electronic components. AESA (active electronically scanned array) radars used on modern warships and fighter airplanes can not be made without those metals. China produces some 95% of those available on the global market.

It will take one or two years until the currently available stocks outside of China are diminished. But it takes much longer to open up new mining and processing facilities for replacement of the Chinese production. The processes used therein are quite dirty. A not-in-my-backyard attitude will make any setup of new facilities difficult to pursue.