Armed terrorists took over Chernobyl power plant. You are the countermeasure.
To pay such amount of money to the extremists is unthinkable. Frontal attack, however, could not be thought about, either - the terrorists would have executed their plan if they saw attacking forces.
There were too many of them and too well equipped for a quick military operation to succeed.
One possibility remained - to select the best Spec Ops single unit to sneak in and destroy enemy installation, preventing them from blowing up the Chernobyl and killing as many of them as possible. One man.