The "classification" issue and the "war plans" semantics are largely a red herring.
Here's the primary law at issue:
>>>
18 U.S. Code § 793 - Gathering, transmitting or losing defense information . . .
(f) Whoever, being entrusted with or having lawful possession or control of any document, writing, code book, signal book, sketch, photograph, photographic negative, blueprint, plan, map, model, instrument, appliance, note, or information,
relating to the national defense, (1) through gross negligence permits the same to be removed from its proper place of custody or delivered to anyone in violation of his trust, or to be lost, stolen, abstracted, or destroyed . . . Shall be fined under this title or imprisoned not more than ten years, or both.<<<
www.law.cornell.edu
Here are the pertinent questions under the law:
First question: Does the timing of the F-18 and drone strikes constitute "information . . . relating to the national defense"?
Second question: Did any of the people in the Signal chat group "through gross negligence" permit it to be removed or delivered to anyone in violation of his trust?
Hillary Clinton avoided criminal charges by the skin of her teeth because Comey determined that gross negligence actually requires intent:
>>>All the cases prosecuted involved some combination of clearly intentional and willful mishandling of classified information, or vast quantities of materials exposed in such a way as to support an inference of intentional misconduct, or indications of disloyalty to the United States… We do not see those things here.<<<
On July 5, FBI Director James Comey announced that he was not going to recommend the filing of criminal charges against Hillary Clinton over her use of a
warontherocks.com
Hegseth can make a pretty strong argument that he cannot be charged with a crime if the Clinton intent standard is applied to the facts of Signalgate situation.
On the other hand, if the FBI were to apply a "complete dumb*ass" standard instead of intent, he's toast (that's a joke)(not a funny joke, just a joke)