条件・譲歩N2
〜上は
now that... (one must...)
Structure
V-辞書形／た形 + 上は
Explanation
Similar to 〜以上(は): "now that one has done something, one should..." Stronger in tone and more literary or formal. Attached to the dictionary/ta-form of verbs.
Examples
引き受けた上は、最後まで責任を持ってやり遂げるつもりだ。
Now that I've taken it on, I intend to see it through to the end.
受験を決めた上は、どんなに苦しくても頑張ろう。
Since we've decided to take the exam, let's do our best no matter how hard it gets.
Note
上は is more literary than 以上(は); the main clause expresses resolve or obligation. Don't confuse it with 〜上で ("after doing").