in (e.g. secret); with (e.g. success)
「裏」 has another reading with different meanings.
opposite side; bottom; other side; side hidden from view; undersurface; reverse…
(with a) successful outcome; (ending in) success
secretly; covertly; tacitly
二つの事柄は表裏一体の関係だ。
There is an inseparable relationship.
裏面を確認してください。
Please check the back side.
裏工作が行われていたらしい。
It seems behind-the-scenes maneuvering was going on.