troubled times; turbulent era
Refers to a historical period marked by war, disorder, or social upheaval. Often used in contrast with 治世 (peaceful reign).
戦国時代は長い乱世だった。
The Warring States period was a long era of turmoil.
乱
Wisdom to survive turbulent times is required.
turbulent times; war-torn era
Compound of 乱 (disorder) and 世 (world, era). The reading らんせい is the standard on'yomi.