  We address a problem of area protection in graph-based scenarios with
multiple mobile agents where connectivity is maintained among agents to ensure
they can communicate. The problem consists of two adversarial teams of agents
that move in an undirected graph shared by both teams. Agents are placed in
vertices of the graph; at most one agent can occupy a vertex; and they can move
into adjacent vertices in a conflict free way. Teams have asymmetric goals: the
aim of one team - attackers - is to invade into given area while the aim of the
opponent team - defenders - is to protect the area from being entered by
attackers by occupying selected vertices. The team of defenders need to
maintain connectivity of vertices occupied by its own agents in a visibility
graph. The visibility graph models possibility of communication between pairs
of vertices.
  We study strategies for allocating vertices to be occupied by the team of
defenders to block attacking agents where connectivity is maintained at the
same time. To do this we reserve a subset of defending agents that do not try
to block the attackers but instead are placed to support connectivity of the
team. The performance of strategies is tested in multiple benchmarks. The
success of a strategy is heavily dependent on the type of the instance, and so
one of the contributions of this work is that we identify suitable strategies
for diverse instance types.
