According to a Defense Science Board (DSB) report, the vulnerability of U.S. military communications satellites is a "reality that should be considered a crisis to be dealt with immediately."
These satellites run the risk of being rendered inoperable through jamming, cyber attack, and possibly laser attacks, especially by the Chinese military, which has demonstrated those capabilities. (In a recent development, the U.S. Defense Intelligence Agency set up a "counter-space office" to track Chinese and Russian developments in space warfare.)
"Under severe stress situations, jamming can render all commercial SATCOM and most defense SATCOM inoperable, except for the low- and medium-rate modes of defense extremely high frequency" satellite communications.
In a conflict, reduced satellite communications could disrupt command and control, global communications, communications between aircraft and ships, targeting, and every user of military satellite communications -- which is to say, a great deal of the U.S. military.
In a separate report, the DSB also noted that US leaders should prepare for greater challenges to global air superiority, which the U.S. has enjoyed for most of the past 70 years.
Instead of expecting air superiority in the battlespace at all times, the military should realistically look at "on-demand air superiority," where the US is able to achieve superiority in limited areas and for limited amounts of time. This shift is due largely to increasing adversary capabilities and air assets that are stretched thin across the globe. This will increasingly be the case once militaries employ armed UAVs and "suicide drones" against U.S. air bases and traditional air power.