This is the 10309th most frequent Russian word.
бронеавтомобилей
Armored vehicles.
"Бронеавтомобилей" is used in the genitive case to specify the type of vehicles being discussed, in this case, many armored vehicles.
В ходе учений военные использовали множество бронеавтомобилей.
During the exercises, the military used numerous armored vehicles.
"Бронеавтомобилей" is in the genitive plural form here to denote that the activity (production) pertains to these vehicles.
Производство бронеавтомобилей является важной отраслью промышленности.
The production of armored vehicles is an important industry.
"Бронеавтомобилей" is in the genitive plural form, referencing the type of vehicles in the convoy.