मध्यमस्यात्मा तृतीया पञ्चमी च प्रकृती प्रकृतयः ॥ कZ_०७.१८.०१ ॥
madhyamasyātmā tṛtīyā pañcamī ca prakṛtī prakṛtayaḥ
For the middle king (madhyama), his own side—namely the third and the fifth constituent factors—are the natural (aligned) factors.
To provide a rule-of-thumb for alliance orientation: which power-centers are structurally likely to align with the middle king in a triadic rivalry.