also: ちょせん
noun
beginning of hostilities; opening of a conflict
Refers to the initial stage of a war, battle, or military campaign. Often used in historical or news contexts.
緒戦の勝利がその後の戦局を大きく左右した。
The victory at the beginning of hostilities greatly influenced the subsequent course of the war.
noun
Used in sports or competitions to mean the first match of a series, tournament, or season. Synonymous with 初戦.
See also: 初戦
緒戦で強豪チームと当たることになった。
We ended up facing a strong team in the first match.
初戦 is more common for 'first match' in sports; 緒戦 can also mean 'beginning of hostilities' and is slightly more formal/literary.
Compound of 緒 (beginning, thread) and 戦 (war, battle). The reading しょせん is the standard Sino-Japanese reading; ちょせん is a less common variant.