This is the 2006th most frequent Russian word.
усилиям
The Russian word "усилиям" (dative plural of "усилия") means "efforts" or "endeavors" in English.
The word 'усилиям' is in the plural dative case here, showing that success is a result attributed to the 'efforts'.
Мы добились успеха благодаря общим усилиям.
We achieved success thanks to joint efforts.
Here, 'усилиям' is in the plural dative case, indicating that 'efforts' are necessary for this situation.
Требовалось приложить много усилий, чтобы решить эту проблему.
A lot of effort was required to solve this problem.
In this sentence, 'усилиям' is in the dative case as it is a complement, directed towards whom gratitude is being expressed.