Pentagon.
While Xuehu was stirring up chaos in the Western Pacific, it was still early morning in America, a time when the staff had just entered their working state, but now it was already past midnight.
Nuclear war alerts hadn't caused too much panic here, as a quick glance at the satellites would reassure them that things weren't so far out of hand.
The launch of an intercontinental ballistic missile could be identified by its extremely strong and unique infrared signature. Sensing satellites simply needed to spot a large heat source moving at thousands of kilometers per hour to trigger an alert.
If, after tracking its trajectory, the target was suspected to be on domestic soil or that of an ally, it would then generate the highest level of warning.
However, the heat signature of Xuehu's flight was far less significant than a rocket's trail, especially after special treatment, and only the nearby, too-late-to-evaluate Pacific Fleet was briefly thrown into confusion.