I think Irregular Warfare or Irregular Operations would be a good general title. Naturally, it would be a good idea for the person posting the message to add the theater of operations.

The definitions of irregulars and guerrillas described in the publication of GENERAL ORDERS NO. 30 by Gen. Curtis may be useful. At least this is the way the United States authorities in Missouri operating under marshal law defined these type of irregular forces. Curtis was removed from command of the department shortly after the publication of the order.

HEADQUARTERS DEPARTMENT OF THE MISSOURI,
St. Louis, April 22, 1863.
General Orders,
No.30.

To warn the public of the severe penalties which will follow new transgressions in this Department, and for the convenience of District Commanders, Judge Advocates, and Military Courts, the following laws of war and general instructions are prescribed.
Judge Advocates will be governed accordingly, in drawing their charges, and Military Courts in their findings, throughout this Department.
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III. GUERRILLA. - Under the general term of Guerrilla will be more particularly considered:

1st. Military Insurgents or War Rebels. - The war rebel is defined by Lieber as follows: " Similar remarks (referring to those given under the preceding head) apply to the rebel, taking the word in the primitive meaning of rebellare, that is, to return to war after having been conquered; and to conspiracies, that is, secret agreements leading to such re-assumption of arms in hands of whatever number, or, which is still worse, plans to murder from secret places.

"The war rebel has been universally treated with the utmost rigor of the military
law. He exposes the occupying army to the greatest danger, and essentially interferes with the mitigation of the severity of war, which is one of the noblest objects of the modern law of war to obtain. Whether the war rebel rises on his own account, or whether he has been secretly called upon by the enemy to do so, would make no difference whatever."

And particular attention is further called to the following extract from a letter of
instructions, addressed by the General-in-Chief to the Commanding General of this Department:

"All of Missouri is now in the military occupation of the United States. The inhabitants are therefore bound by the laws of war (without any regard to their civil allegiance to the Government of the United States, as the sovereign power,) to render obedience to the occupying military authority. If they take up arms in insurrection, or render aid and assistance to the enemy, they become military insurgents or military traitors, and thereby forfeit their lives and property. Every one who was not in arms at the time of the occupation and who has not continued in arms, but who subsequently takes up arms within the territory militarily occupied by us, is not to be regarded as a prisoner of war, but is to be punished as a military insurgent. So every one, be he a citizen of Missouri or not, who comes within our lines as a non-combatant, and afterwards takes up arms, is a military insurgent."

The above remarks are applicable to all other parts of this Department now in the military occupation of the United States.
Officers or men sent by the enemy within our lines to recruit, thereby inciting
insurrection, become themselves (when not actual spies) military insurgents. Such also are Knights of the Golden Circle, and members of other secret organizations looking to any opposition to the laws of the United States, being in the nature of conspirators.

Whoever shall be convicted as a military insurgent shall suffer death, according to the usages of nations, by sentence of a Military Commission.

2d. The Partizan. - "The partizan corps designates bodies detached from the main army. * * * * The partizan leader commands a corps whose object is to injure the enemy by action separate from that of his own main army; the partizan acts chiefly upon the enemy's lines of connection and communication, and out-side of or beyond the lines of operation of his own army, in the rear and on the flanks of the enemy. Rapid and varying movements and surprises are the chief means of his success; but he is part and parcel of the army, and, as such, considered entitled to the privileges of the laws of war, so long as he does not transgress them."

Partizan soldiers must have the organization and equipment of soldiers, or they are brigands or guerrillas, and will be punished as such.

3d. The Brigand.- "The brigand is, in military language, the soldier who detaches himself from his troop and commits robbery, naturally accompanied in many cases with murder and other crimes of violence. His punishment, inflicted even by his own authorities, is death. The word brigand, derived as it is from brigner, to beg, meant originally beggar, but it soon came to be applied to armed strollers, a class of men which swarmed in all countries in the middle ages. The term has, however, received a wider meaning in modern military terminology. He that assails the enemy without or against the authority of his own government is called, even though his object should be wholly free from any intention of pillage, a brigand, subject to the infliction of death, if captured.

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Whoever shall be convicted as a brigand, no matter whether of our own forces or those of the enemy, shall suffer death, according to the usage of nations, by sentence of a Military Commission.

4th. The Guerrilla Proper. - Guerrillas proper may be defined as "troops not belonging to a regular army, consisting of volunteers, perhaps self-constituted, but generally raised" (within the lines of the enemy as a contra-distinction from military insurgents) "by individuals authorized to do so by the authority they acknowledge as their government. They do not stand on the regular pay-roll of the army, or are not paid at all, take up arms and lay them down at intervals, and carry on petty war chiefly by raids, extortion, destruction and massacre, and who cannot encumber themselves with many prisoners and will therefore generally give no quarter. They are peculiarly dangerous, because they easily evade pursuit, and by laying down their arms become insidious enemies; because they cannot otherwise subsist than by rapine, and almost always degenerate into simple robbers or brigands."

Whoever shall be convicted as a guerrilla under this order, shall suffer death, according to the usage of nations, by sentence of a Military Commission.

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