After years of building tension and deferred conflict, World War III breaks out. Multiple factions across the Earth foment the deadliest war in human history, with the unprecedented widespread use of nuclear weapons on several continents.
Ships from six different nations clash in the first large scale orbital engagement in human history, easily dwarfing the minor Sino-American Orbital Skirmish. Orbital ships and positions used to conduct bombardments of Earth and Luna.
US and PLA marines clash over lunar colonies, resulting in catastrophic pressurization failures and the death of many civilian lunar colonists.
Mars is untouched by the war, but loses contact with NASA, ESA, and private sponsors on Earth. No more resupply ships arrive, and the colony must assume the worst.