Consider the following premises. For all x_1, if x_1 drinks water, then x_1 is a soldier. There is at least one x_1 for which if x_1 were a soldier, then x_1 is sleeping. For all x_1, if x_1 sleeps, then x_1 is drinking water. Can we infer the following from them? There is at least one x_1 for which x_1 is a soldier if and only if x_1 will sleep.
 From the fact that for all x_1, if x_1 sleeps, then x_1 is drinking water, and that for all x_1, if x_1 drinks water, then x_1 is a soldier we can infer that for all x_1, if x_1 sleeps, then x_1 is a soldier. Finally, from the fact that there is at least one x_1 for which if x_1 were a soldier, then x_1 is sleeping, and that for all x_1, if x_1 sleeps, then x_1 is a soldier we can infer that there is at least one x_1 for which x_1 is a soldier if and only if x_1 will sleep. Therefore, the answer is yes.