What event occurred first in the sequence of significant attacks related to U.S. security issues?

The significant attacks related to U.S. security issues have various timelines, and when looking at the events listed, the bombing in Mumbai is the first to occur in chronological order. The series of attacks in Mumbai took place from November 26 to November 29 in 2008 and involved multiple locations, resulting in numerous casualties and drawing international attention to terrorism.

In contrast, the other events occurred later: the Fort Hood shooting happened in November 2009, the Boston Marathon bombing took place in April 2013, and the formation of the U.S. Cyber Command was established on June 23, 2010. This sequence of dates indicates that the Mumbai attacks predate the other events, thereby making them the earliest incident related to U.S. security concerns.