When one of the five planets Mercury, Venus, Mars, Jupiter, or Saturn are within 1 degree of one another then they are said to be in a planetary war, or graha yuddha. The Sun, Moon, and the nodes of the Moon, Rahu and Ketu are excluded. These basic points are generally agreed upon by astrologers. However, there is not any uniform agreement about what the factors are that determine which planet wins the war, or about the effects on the planet who wins or loses.
Some will say that the planet with lower degrees or longitude wins the war. This is most commonly followed rule in my experience. Others will say that it's the planet of higher degrees. Other texts will stress that it's not about longitudinal degrees but latitude north or south of the ecliptic. The planet that is northerly will win the war. More confusing yet, others speculate that this refers to northerly declination not latitude. Declination is the distance a planet travels from the celestial equator. For instance, the Sun will be at its highest point of declination, about 23 degrees on the summer solstice. However, the Sun is always at 0 degrees latitude. Declination and latitude become difficult to determine because some ephemeris's and software programs will not give the latitude or declination, only longitude. There are also classical references supporting the planet that's the brightest visibly as winning the war. In this case, Venus always wins the war since it's the brightest planet.
The effects of planetary war is still another issue. Some will say that both planets suffer just like both countries suffer in a war. Others say that the victor takes over the significations of the loser just like the winning country will hoard the losing country's resources.
Sometimes translations of classic texts will also make the issue confusing. Take, for instance, the following two translations of the same verse from the Brihat Parashara Hora Shastra about planetary war:
"There is a planetary war if Mars, Mercury, Jupiter, Venus, and Saturn are together (within one degree of each other), Venus is the conqueror whether he is in North or South, but amongst the other four only one, who is in the North is the conqueror and that in the South is considered defeated in the planetary war."
- Ch. 81 v. 9.
"Should there be planetary war between Mars etc. planet and if Venus happens to be in the North or in the South, it becomes victorious. The conjunction of the other planets within one degree causes planetary war and the planet only in the north - i.e.having higher celestial longitude is reckoned as stronger and becomes victorious." - Ch. 81 v. 9.
The second translation equates higher longitude with higher latitude. I'm not convinced that this is a proper translation. In thePhaladeepika, it supports the idea of latitude not longitude:
"Planets posited in the north, possessing brilliant rays, should be considered as victorious in planetary war." - Ch. 4 v.2
Hart DeFouw's book, Light On Life, also supports this concept:
"Whichever planet has the higher latitude is declared the winner and is strengthened thereby, while the loser is weakened. Many modern books on Jyotish, however, take the planet with the lower longitude to be the victor. A planet's latitude can be found in tabulated form in a Panchanga (an Indian Ephemeris), but this is usually missing from a Western ephemeris." p. 65
As you can see planetary war is a controversial and confusing issue. I am still undecided about it personally. For a long time I've used the general rule that the planet with the lowest degrees wins. This seems to work in many cases. But recently I've found these references from classic texts that indicate other rules to follow.
After all the speculation is said and done, the answers should be obvious based on practical example, which we'll explore in tomorrow's article: An Infamous Case of Planetary War