This is a special factor that only comes into play when planets (not including the Sun and Moon) are located within one degree of each other. As per the rules of planetary war, the planet with the lower position in degrees and minutes wins. By other accounts, the planet with the higher declination (further north relative to the ecliptic) wins.
Points are added to the victor and subtracted from the loser according to the amount of strength of the planet generally and the relative size of its disc.Planets can gain or lose significantly by planetary war, but the nature of the planets also comes into play here.
Venus would lose more in a Planetary War with Mars than with Mercury, as it is generally an enemy of Mars but a friend of Mercury. Generally, I don't rate planetary war very highly by itself but look more at the nature of the conjunction by the natural and temporal statuses of the planets involved.