The text you've been given is not well written.The text really needs correction before you can fill in that blank.
The first sentence is incorrect for starters.
There's several correct possibilities. One is:
"A new company of soldiers is being sent to the conservation area to join the battle against illegal hunters."
In the 2nd sentence, the present tense of 'hunt' is very awkward to the point of being incorrect as well. 'valuable' is incorrect in this context too.
I'd rewrite the sentence as,
"Authorities have reported that ruthless poachers have been hunting elephants for the value of their tusks."