No trial is required. You are not operating under civil law - but rather, the laws of war.
"Art. 3.
Martial Law in a hostile country consists in the suspension, by the occupying military authority, of the criminal and civil law, and of the domestic administration and government in the occupied place or territory, and in the substitution of military rule and force for the same, as well as in the dictation of general laws, as far as military necessity requires this suspension, substitution, or dictation.
The commander of the forces may proclaim that the administration of all civil and penal law shall continue either wholly or in part, as in times of peace, unless otherwise ordered by the military authority.
"Art. 4.
Martial Law is simply military authority exercised in accordance with the laws and usages of war. Military oppression is not Martial Law: it is the abuse of the power which that law confers. As Martial Law is executed by military force, it is incumbent upon those who administer it to be strictly guided by the principles of justice, honor, and humanity - virtues adorning a soldier even more than other men, for the very reason that he possesses the power of his arms against the unarmed.
Art. 5.
Martial Law should be less stringent in places and countries fully occupied and fairly conquered. Much greater severity may be exercised in places or regions where actual hostilities exist, or are expected and must be prepared for. Its most complete sway is allowed - even in the commander's own country - when face to face with the enemy, because of the absolute necessities of the case, and of the paramount duty to defend the country against invasion.
To save the country is paramount to all other considerations."
The commander is given a wide latitude to be as severe as necessary. He has the necessary authority to put someone to death (#12). There is another article (#17) that states it is okay to starve your enemy to end the war sooner. Furthermore, the Articles of War are designed for matters dealing with unarmed civilians or uniformed combatants. Spies, partisans, and guerrillas need not apply.
I think LG's just pinged the heart of your position and this only affirms it. You simply cannot justify or fully defend Lincoln under the guise of the Constitution, so rather than concede a fault you take to defending the indefensible and celebrating those who THROW OFF the Constitution in favor of pure military despotism. Stalin would be proud of you.