“True Warrior Decoction” is mentioned in the Shang Han Lun only twice. The first time it is mentioned, it is in reference to Tai Yang disease:
太陽病,發汗,汗出不解,其人仍發熱,心下悸,頭眩,身瞤動,振振欲擗地者,真武湯主之。
"In Tai Yang disease, when there is sweating, and the emergence of sweat does not resolve the disease, and the person still has fever, there are palpitations below the heart, the head is dizzy, and the body shivers violently, and they are quivering and about to fall on the ground, Zhen Wu Tang governs it."
In this scenario, the person is sweated with Gui Zhi Tang and the person does not recover or the person has sweated themselves and has not recovered. In both cases, the person has a yang deficiency because the person’s yang qi with the addition of a correct treatment of Gui Zhi Tang is still too weak to defeat the pathogen. Because of this yang deficiency, there is cold shivering, and because the body is attempting to mobilize its yang qi to the surface, there isn’t enough left to maintain the interior, so the Shao Yin heart and head begin to feel the effects.
The second time Zhen Wu Tang is mentioned is in reference to Shao Yin disease:
少陰病,二三日不已,至四五日,腹痛,小便不利,四肢沉重疼痛,自下利者,此為有水氣,其人或欬,或小便利,或下利,或嘔者,真武湯主之。
In ShaoYin disease, that has lasted two or three days without stopping, and at four or five days, there is abdominal cramping, inhibited urination, heaviness and pain of the four limbs, and spontaneous diarrhea, this is because the person has water qi, and the person may have cough, or uninhibited urination, or diarrhea, or retching, then Zhen Wu Tang governs it.
Zhen Wu Tang:
Fu Ling 3 Liang (45g)
Shao Yao 3 Liang (45g)
Bai Zhu 2 Liang (30g)
Sheng Jiang 3 Liang (45g)
Fu Zi 1 piece prepared
*if cough add:
Wu Wei Zi half sheng (100mL)
Xi Xin 1 Liang (15g)
Gan Jiang 1 Liang (15g)
*if urine flows freely, remove Fu Ling
*if there is diarrhea, remove Shao Yao and add 2 Liang of Gan Jiang
*if there is retching, remove Fu Zi and Sheng Jiang to equal 8 Liang (1/2 Jin).
In the first description of symptoms in Shao Yin disease, there are Earth symptoms being inversely invaded by Water: abdominal cramping (Wood trying to control the Water in the Earth), inhibited urination (Water being directed towards the Earth element), heaviness and pain of the four limbs (the Earth rules the four limbs), and spontaneous diarrhea (Water invading the Earth Spleen).
In the second description of the symptoms the Metal is overwhelmed by Water, and cough and uninhibited urination occur (or perhaps constant urination from the Lung being too open and a lack of pressure within the system). Also there is Earth disharmony as the Stomach is in counterflow, leading to collapse of the Spleen.
In both cases, the method is to restore the yang of the Kidney and drain the excess water to correct the reversal of Water Qi invading Metal and Earth. In the Tai Yang example, we can note that the Zhong Qi (中氣) of Tai Yang is Shao Yin and the Zhong Qi of Shao Yin is Tai Yang. This is an explanation for why, if someone is severely deficient and they are subjected to Tai Yang disease, and sweating does not work, that a Shao Yin pattern emerges. The ying and the wei have as their source the ultimate yang and yin of Shao Yin, when these are severely depleted the patient cannot mount an attack even with sweating so the underlying yang deficiency must be addressed with Fu Zi.