This is the 17613th most frequent Russian word.
тылу
"Тылу" (dative form of "тыл") means "to the rear" or "to the back" in a military or geographical context.
Тылу in this context means 'in the rear' referring to working behind the front lines.
Моя бабушка вспоминала, как она работала в тылу во время войны.
My grandmother recalled how she worked in the rear during the war.
Here, тылу refers to 'in the rear' of a military position.
Он создавал защиту в тылу армии.
He was establishing defenses in the rear of the army.
Here, тылу is used to mean 'in the rear' in a general logistical sense.