If you look at the Scoreboard, you’ll see a column entitled “Military Score”. During the early part of the game, when there’s a limited number of starbases in play, it’s quite possible to use that score to analyze the enemy fleet. Even in the later game, it’s quite possible to use it to figure out builds and ship trades by your enemies.

Here’s a short description of the method:

At the beginning of the game, most of us are at 2110; that’s the value of our planetary defenses and initial starbase combined. A lot of players begin the game building freighters, and ships without guns don’t add to the score. The Empire gets some automatic fighters and some people will build the odd defense point. Apart from that, any increase from turn to turn is probably the value of any warship built.

This is the documentation on the Military Score formulas:
http://play.planets.nu/#/howtoplay/military-score

The following is an example of an exact determination made on the second turn of a real game, which revealed the first-turn construction of a player. Bear in mind that it required some research and an educated guess.

The Colonial player stands out from the crowd: 3988 is his total score, where most of the other players are still at 2110. Detract the 2110 that everyone else has, and if he didn’t buy any defense, his ship cost 1878.

A bit of research showed that, in his last game as Colonies, that player built a transwarp Cobol. Let’s price that out:

Transwarps cost 300 each plus 54 minerals; each is 300 + (54)x(5) = 570 for a total of 1140.

A Cobol hull costs 150 and 92 mins = 610.

If we presume the preceding is true, his armament total must therefore cost 128.
XRays x4 = 28.
Mk4 x2 = 100.

Therefore, our Colonist built a Cobol with XRays and Mk4s. Just like in his last game.

Of course, that one was a very simple determination; you might even say it’s cheating, since that’s what he usually builds. What’s more, if he built even one or two planetary defense posts, it would have thrown off the math by half a dozen points. That’s why, on later turns, it’s often very difficult to get a precise answer. Even so, if you keep track of some basic numbers, you can often make a decent estimation of a player’s fleet. The following is an example from a completely different game.

It’s rather late in this game, and the Cyborg player owns 58 planets, 56 of which have starbases. Because the Cyborg is fighting against several players, we’ve got a fair picture of his empire, and we can count his minefields. What’s more, since he’s been aggressively fighting along one front and is exposed to cloaking infiltration along the other, we can also presume that most of his starbases are fully defended and on fairly populous planets. His military score is about 720000.

A starbase with 200 defense points and 60 fighters is valued at

Starbase defense costs 1d and 10mc, which totals 15 points — halved, because it’s fixed in position. 200 defense, therefore, rates 1500 points.

Fighters cost 100mc plus 5 minerals, which totals 125 points — again, these are halved. 60 fighters, then, rates 3750 points.

There’s almost always between 60 and 200 defense posts on the ground under a defended starbase, and usually more on a well-populated Cyborg world. A quick look at one of that player’s previous games gives us the information that he averaged about 150 at that point in the game. That works out to 825 points per planet.

So the starbase total here, at 4575 points per base, is at most 256200 points; it’s probably a bit less, considering that some of the backwater planets may well not be fully defended.

Next, the minefields: There were quite a large number of mines in each of a dozen huge fields. Each mine works out to .355 points; there were over 350000 mines laid in the identity of the Cyborg player, which adds up to about 125000 points, give or take.

From these numbers, we can show that his fleet is somewhere around 350000 points. It numbers 72 ships, 14 of which are freighters, leaving 58 warships of various sorts.

Again, having researched this Cyborg player, we can see that he rarely builds Annihilations as his main warship, preferring to rely on Biocides. On these, he often kept between 120 and 140 fighters, and more if he could afford them. Even on his early ships he tends to pay for transwarp engines, and he varies between Disruptors, Positron Beams, Blasters, and Heavy Blasters.

So each fully-armed Biocide from early in the game, we can figure, runs around 27000 points; late-game Bios run about 5000 more. Bear in mind that there’s a ton of variation if the player loads more fighters.
(Weapons: 800-1660 for the basics; 6400 for Heavy Phasers
6125 for the hull
130 fighters @125 = 16250
6 transwarps @570 = 3420)

A similar calculation for Fireclouds gives a very wide variety of scores, from 1250 up to 6250. About half of them are likely on the low end; the majority won’t have serious armament, since Fireclouds are used mostly for transportation instead of combat. For ease of calculation, I’m going to go with 2500 points per.

There’s also a fair quantity of points that have likely been invested in at least one Merlin and Neut Refinery. Since those also are rarely well-armed or given transwarp engines, we’d be safe at a 6000-7000 point guess per; we’ll call it 13000 for a pair. Again, it’s worth checking the player’s previous games to see whether he prefers to arm them at all; some players don’t.

Finally, we can presume that, since the Cyborg player is actively engaged in minelaying, that he likely has a few hundred torpedoes ready to lay as mines. I’m going to guess a couple of hundred Mk7s at 51 points each, for about 10000 points total.

If we act on the presumption that the armed Cyborg fleet consists of one Refinery, one Merlin, and 56 other ships divided between Biocides and Fireclouds, we can use these numbers to give us a decent guess as to how many of each he owns. Remember we have a total of around 350000 points, from which we deduct 10000 for torpedoes and 13000 for the factory ships, leaving 327000.

Using B as the number of Biocides and F as the number of Fireclouds, we can state the following formulae:
27000 B + 2500 F is about 327000
F + B = 56

This shows that he probably has between seven and nine Biocides.

Now, here’s one reason this comes in handy: During the course of this game, we’ve actually seen twelve Biocides that are still active. The only way this is possible is if we’ve overestimated somewhere. Looking back, we can presume at least a couple of them have low-end engines, but that only frees up 15000 points. The only category that permits a huge variance like this is the number of fighters. My conclusion, then, is either that only six or seven of those Biocides carries a full load, or several of his starbases are underdefended. Therefore, it might be a wise idea to move aggressively against the Cyborg, forcing his fleet to deploy for battle.

A final note: It’s never wise to rely on this sort of thing absolutely. Even in the early game, such minor dodges as building random torpedoes, defenses, fighters, or what have you at various spots can seriously alter the numbers. Trades can be disguised in the mid-to-late game by the simple expedient of ballasting some with torpedoes or by laying and scooping minefields. However, if you’re at least aware of the technique, that gives you the knowledge to mess with other people using it — and if other people don’t bother to read the guides, you’ve got a solid intel advantage.

Good hunting, folks!