  This paper provides a decomposition technique for the purpose of simplifying
the solution of certain zero-sum differential games. The games considered
terminate when the state reaches a target, which can be expressed as the union
of a collection of target subsets; the decomposition consists of replacing the
original target by each of the target subsets. The value of the original game
is then obtained as the lower envelope of the values of the collection of games
resulting from the decomposition, which can be much easier to solve than the
original game. Criteria are given for the validity of the decomposition. The
paper includes examples, illustrating the application of the technique to
pursuit/evasion games, where the decomposition arises from considering the
interaction of individual pursuer/evader pairs.
