द्विगुणान्तरं त्रिगुणान्तरं वा व्यूहेत ॥ कZ_१०.५.०४ ॥
dviguṇāntaraṃ triguṇāntaraṃ vā vyūheta
Or he should array them with double spacing, or triple spacing.
When terrain is open, when maneuver space is needed, when facing missiles/elephants/chariots, or when avoiding congestion and chain-reaction disorder.