This is the 70th most frequent Russian word.
обороны
"Обороны" means "defense" in English.
In this sentence, 'обороны' serves as a noun in the genitive case to specify the purpose for strengthening.
Для укрепления обороны страны установили новые меры.
To strengthen the country's defense, new measures were implemented.
Here, 'обороны' is used as a noun in the genitive case, indicating the specific type of plan.
Он занимался разработкой плана обороны города.
He worked on the development of the city's defense plan.
In this example, 'обороне' is used as a noun in the dative case as part of a legal or formal context.