No agency created by a power of attorney in writing given by a principal who is at the time of execution, or who, after executing such power of attorney, becomes either (1) a member of the armed forces of the United States, or (2) a person serving as a merchant seaman outside the limits of the United States, included within the forty-eight states and the District of Columbia; or (3) a person outside said limits by permission, assignment or direction of any department or official of the United States government, in connection with any activity pertaining to or connected with the prosecution of any war in which the United States is then engaged, shall be revoked or terminated by the death of the principal, as to the agent or other person who, without actual knowledge or actual notice of the death of the principal, shall have acted or shall act, in good faith, under or in reliance upon such power of attorney or agency, and any action so taken, unless otherwise invalid or unenforceable, shall be binding on the heirs, devisees, legatees, or personal representatives of the principal.