Week by week little encounters increased; it was apparent that _ were steadily growing bolder.

Explanation

"Week by week little encounters increased; it was apparent that the Turks were steadily growing bolder."Here's why:- "the Turks" refers to a specific group of people, implying that the encounters were with the Turkish people or forces.- The definite article "the" indicates that the sentence is referring to a particular group, previously mentioned or known.