  We study the optimal control problem of minimizing the convergence time in
the discrete Hegselmann--Krause model of opinion dynamics. The underlying model
is extended with a set of strategic agents that can freely place their opinion
at every time step. Indeed, if suitably coordinated, the strategic agents can
significantly lower the convergence time of an instance of the
Hegselmann--Krause model. We give several lower and upper worst-case bounds for
the convergence time of a Hegselmann--Krause system with a given number of
strategic agents, while still leaving some gaps for future research.
