Planetary war (graha yuddha) is declared where two planets are in close proximity; one is victorious or defeated according to the consideration of superior strength.
Verse 2 — Criteria of Victory in Graha Yuddha
दीप्तिमांस्त्वुत्तरस्थो वा बृहत्तमोऽपि वा ग्रहः । युद्धे स जयति नित्यं पराजितस्तदन्यथा ॥
dīptimāṁs tv uttarastho vā bṛhattamo 'pi vā grahaḥ | yuddhe sa jayati nityaṁ parājitas tad anyathā ||
The planet that is brighter, or stands farther to the north, or is larger in apparent size, always wins the war; otherwise it is defeated.
parājitasya daśāyāṁ tu tat-phalaṁ nopajāyate | dhanakṣayaḥ svajanakṣayaḥ śarīraduḥkham eva ca ||
During the dasha of the defeated planet its promised results fail to materialize; there is loss of wealth, harm to one's own people, and bodily suffering.