This is the 9261st most frequent Russian word.
союзе
"In the union" (prepositional case of "союз").
The word 'союзе' here is used to refer to the proper noun 'Советский Союз' (the Soviet Union), indicating the location.
Мы жили в Советском Союзе.
We lived in the Soviet Union.
Here 'союзе' is used to mean 'union' or 'partnership,' referring to the collaboration or association.
Наш успех произошел в союзе с другими организациями.
Our success happened in partnership with other organizations.
In this usage, 'союзе' metaphorically describes the combination or connection of concepts or actions.