序盤(じょばん)the opening(s) (e.g. in a game of go or chess)

囲碁(いご)の序盤(じょばん)が終(お)わり、中盤(ちゅうばん)に突入(とつにゅう)した。

The opening of the Go game has ended, and it has entered the middle game.

選挙(せんきょ)戦(せん)はまだ序盤(じょばん)なので、結果(けっか)は分(わ)かりません。

The election campaign is still in the opening stages, so the result is unknown. {the opening(s) (e.g. in a game of go or chess)}

試合(しあい)の序盤(じょばん)は好調(こうちょう)だったが、中盤(ちゅうばん)で形勢(けいせい)が逆転(ぎゃくてん)した。

The opening of the match was going well, but the situation reversed in the middle game. {the opening(s) (e.g. in a game of go or chess)}

序盤(じょばん)で諦(あきら)めてしまったら、中盤(ちゅうばん)でも終盤(しゅうばん)でも、逆転(ぎゃくてん)する事(こと)は出来(でき)ません。

If you give up in the opening stages, you won't be able to turn things around in the middle or end game.

応援(おうえん)しているチームが序盤(じょばん)から押(お)されている試合(しあい)を観戦(かんせん)するのは苦痛(くつう)でした。

Watching a game where the team I'm supporting has been under pressure from the opening was painful. {the opening(s) (e.g. in a game of go or chess)}