First Segment

The First Segment was the era marking the beginning of the Last Great Time War. The War Council placed munition factories all over Gallifrey in this period. The War Doctor, who first regenerated in the Fifth Segment, travelled back in time to this period to save Gallifreyan children from a Dalek attack in the munition factory underneath the Mountain of Serenity. (PROSE: The Stranger)

was involved in the First Segment of the Time War. (AUDIO: The Devil You Know)