This is the 6146th most frequent Polish word.
artylerii
"Artylerii" means "artillery" (genitive case) in English.
In this sentence, 'artylerii' is used in the genitive case to indicate support provided by the artillery.
W czasie bitwy ich siły opierały się głównie na wsparciu artylerii.
During the battle, their forces relied mainly on artillery support.
Here, 'artylerii' is in the genitive case, used to denote the subject of the study.
Od długiego czasu studiował historię artylerii.
For a long time, he had been studying the history of artillery.
In this case, 'artylerii' is again in the genitive case, showing possession or relation to the systems being designed.