Near-Earth space is reaching a saturation point, and so, James Clay Moltz suggests, World War III could start in space:
If one tracks current trends and the increasing rate of military spending on space by a variety of countries, one has to worry. These militaries are going to have to engage in mutual restraint if conflict is going to be avoided.
We managed to do so during the Cold War through U.S.-Soviet non-interference pledges, ongoing talks, and a shared belief that satellite security was critical to nuclear stability and arms control. It is less clear that such restraint will prevail in the 21st century. This decade nearly a dozen countries will have the ability to test space weapons and/or attack enemy spacecraft.
Warfare in earth orbit would have lasting side-effects:
China’s 2007 ASAT (anti-satellite weapons) test created over 3,000 pieces of large orbital debris (larger than 4 inches in diameter), which will now continue to hurtle around the Earth at orbital speeds (over 17,000 mph) for some 40 or more years. Or until they finally re-enter the atmosphere and burn up.
Any piece of this debris field could hit a satellite or, worse, a manned spacecraft and cause serious damage, depressurization, and death. A space war involving even just a dozen similar attacks on satellites would create such a large field of hazardous debris that it could render low-Earth orbit too dangerous for astronauts or high-value spacecraft —making near-Earth space essentially unusable.
(Hat tip to Nyrath.)