This is the 11964th most frequent Russian word.
захвату
"Seizure" or "capture" (dative case of "захват").
In this sentence, "захвату" refers to the act of capturing or taking control of a fortress; it's used in the dative case as part of a prepositional construction.
Силы готовились к захвату крепости.
The forces were preparing for the capture of the fortress.
Here, "захвату" indicates the action of taking hold of the chalk and is used in the dative case to express purpose.
Он подошёл к доске для захвату мела.
He approached the board to grab the chalk.
In this use, "захвату" refers to the action of capturing or holding objects, utilized again in the dative case to describe the capability or purpose of the subject.