This is the 1722nd most frequent Russian word.
вражеских
"Вражеских" means "enemy's" or "hostile" (possessive form).
In this sentence, 'вражеских' serves as an adjective describing 'войск' (troops), indicating possession and hostile nature.
Мы успешно отразили атаку вражеских войск.
We successfully repelled the attack of enemy troops.
Here, 'вражеских' modifies 'позиций' (positions), showing that the positions are owned or controlled by the enemy.
Разведчики обнаружили местоположение вражеских позиций.
Scouts discovered the location of enemy positions.
In this context, 'вражеских' qualifies 'сил' (forces), denoting their association with the enemy.