N2 — outside your level filter

上うえは

うえはue waN2literary

savor + (past) + now that

ajiwatta ue wa

now that; given that — a settled fact demands a resolve, said formally

meaning: having savored

こうなった上うえは、最後さいごまで戦たたかうしかない。

kou natta ue wa, saigo made tatakau shika nai.

Now that things have come to this, there's nothing to do but fight it out to the end. neutral

一度いちどお引ひき受うけした上うえは、途中とちゅうで投なげ出だすわけにはまいりません。

ichido ohikiuke shita ue wa, tochuu de nagedasu wake ni wa mairimasen.

Having accepted the task, I cannot possibly abandon it halfway. formal

Same meaning2

now that; given that — leaves no room to turn back

こうなった上うえは、最後さいごまで戦たたかうしかない。
kou natta ue wa, saigo made tatakau shika nai.
Now that things have come to this, there's nothing to do but fight it out to the end. neutral
一度いちどお引ひき受うけした上うえは、途中とちゅうで投なげ出だすわけにはまいりません。
ichido ohikiuke shita ue wa, tochuu de nagedasu wake ni wa mairimasen.
Having accepted the task, I cannot possibly abandon it halfway. formal
委員長いいんちょうをお引ひき受うけした上うえは、誠心誠意せいしんせいい、職務しょくむを全まっとうする所存しょぞんでございます。
iinchou o ohikiuke shita ue wa, seishinseii, shokumu o mattou suru shozon de gozaimasu.
Now that I have accepted the role of committee chair, it is my intention to carry out my duties with complete sincerity. formal

Confined to formal writing and declaimed speech — a ruling, a formal
announcement, a vow. Sounds staged if used in ordinary conversation.