2001

In 2001, the first entries into the Halo universe were released.

May

 * May: Microsoft acquires Ensemble Studios.

August

 * August 15: The approximate origin date for the Beta 1749 build of Halo: Combat Evolved.

October

 * October 30: The novel Halo: The Fall of Reach is released.

November

 * November 15: The Xbox console and the video game Halo: Combat Evolved are released in North America.
 * Halo begins...