Enlightening context for the “warship definition” in this fantastic article by two of the Navy JAG Corps’ best: Commanders Whitehead and Waldo. Highly recommend giving it a read!
“To paraphrase the U.S. Department of Defense Law of War Manual, persons, not inanimate objects such as weapon systems, have rights and obligations under the law of war (§ 6.5.9.3). Vessels designed to attack other vessels are not actors with rights and obligations under the law. They are instead a means of war; they are “weapons or devices used to conduct warfare.” Requiring such vessels to have particular markings during attack supports the general requirement of affirmative distinction. Also, requiring control of force from such vessels by State armed forces ensures attacks are conducted by lawful combatants. As the conduct of war evolves, however, particularly with the continued development of cyber, space, and other information operations, new forms of belligerent acts develop.”