Complex sentence: Neither the monarch nor the viceroy, however, involve themselves in direct military command; per constitutional convention, both must almost always exercise the Royal Prerogative on the advice of the Cabinet, although the right to unilaterally use those powers in crisis situations is maintained.
Split into simpler sentences: Neither the monarch nor the viceroy, however, involve themselves in direct military command. Per constitutional convention, the Crown must almost always exercise the Royal Prerogative on the advice of the Cabinet, although the right to unilaterally use those powers in crisis situations is maintained.