The specific situation is the tech in the Battletech universe. The Kearny-Fuchida hyperdrives are jump drives that can travel instantaneously up to thirty light years - being deposited (usually) at the zenith or nadir jump point of a star system (a spot of minimum gravity several AU from the planets).

The result is that it takes minutes to travel from star system to star system a week-ish to recharge the jump drive, but weeks to months to actually reach a planet.

This gives the BT universe its character - that you don't zip about in a ship hopping from battle to battle. But I wonder about the way combat has been portrayed. If I remember, wars happen mostly along borders. Is that realistic? What strategies would emerge with this model of space travel?

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    $\begingroup$ If your jump points are fairly fixed and predictable, you can assume that battles will often take place near or at jump points. A ship emerging from hyper drive is probably more vulnerable to attack and the jump points also act as supply lines making them very important to guard (sort of like major cities for a rail network). Border fights would only happen because thats the place thats more often patrolled as space is huge and mostly empty. $\endgroup$
    – Shadowzee
    May 9, 2018 at 1:39
  • $\begingroup$ @Shadowzee good point, I'll take a look at the literature and get back to you. I'll update to say - assuming you can't easily choke the jump points depending. My assumption was that space is vast and even though you know ships will generally emerge at a certain point above/below a star, there are still probably a hundred stars in a thirty light year radius to jump to your target from, and the jump point itself is likely an enormous area of space. $\endgroup$
    – user43053
    May 9, 2018 at 3:34
  • $\begingroup$ You're there will be many jump points to defend. Possibly, defenders might guard the most probable points attacking vessels will use. However, it will be extremely difficult to block all of them from letting intruders come through. Perhaps defence might be concentrated around the most critical targets -- planets, space stations, orbital fortresses, & space-based infrastructure. $\endgroup$
    – a4android
    May 9, 2018 at 4:06
  • $\begingroup$ This is a remarkably vague question. What's the nature of the ships/fleets? How likely are the systems to have been around long enough for space stations? What's the tech level? Are the jump points predictable? (they sound like they're not, you said "usually.") There's too much missing info here for a decent answer. Note that simply pointing off-site to (for example) a battletech universe link is unacceptable as links change. Your question should stand alone here. Please visit our help center for more about asking well designed questions. $\endgroup$
    – JBH
    May 9, 2018 at 4:19
  • $\begingroup$ I disagree. I think with a handful of fundamentals about a gameboard, you can get at the principles that drive certain types of strategy - zip to a capital and never tarry in intervening systems, fortify jump points. I've seen similar questions describing a technology and asking how it would affect the military, etc. Anyhow, I'm happy with what's coming in thus far. $\endgroup$
    – user43053
    May 9, 2018 at 4:41

7 Answers 7


Graduation Day

Have a look at Vernor Vinge's novels using bobble technology.

The thing is if space travel becomes so easy and ubiquitous, and anywhere within 30 light year ranges to which then you can just jump another 30 and so on and so on - what will happen?

Suddenly everyone will just jump away, and the human race will disperse radically, there will be no-one left on Earth, and you won't be able to find anyone else. Like the 'technological singularity', an idea Vinge coined, 'Graduation Day' is basically a singularity in which everyone just leaves and disperses so much like gas escaping a balloon.

The actual likely scenario ironically may be that there are no borders at all.

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    $\begingroup$ Wait, what? So you're saying that given the ability everyone just runs as far away from everyone else as they can? If this were true, wouldn't it mean we'd have a lot more hermits living in the mountains with the invention of cars? $\endgroup$ May 14, 2018 at 5:04
  • Each system will have a "border" which can, in principle, be defended. Why keep all your defenses in the inner system, allowing the invader to do all sorts of mischief, if you can send strong detachments to the jump points instead?
    (Fear of defeat in detail might be one reason.)
  • If jump points are "paired" and/or jump lines are relatively few, you might get borders for interstellar polities. If somebody owns both/all ends of a jump line, it is a calculated risk to send only light forces to that jump point. After all, anybody who comes in must have come from one of your systems.
    If ships can jump to any star within 30 lightyears, then it is not feasible to defend or even picket every brown dwarf that could be used as a stepping stone. So you still have to defend the jump points of your systems.

Are you aware of Niven and Pournelle's Mote in God's Eye? Or Weber and White's Starfire books? Warfare along a "jump line" network. With non-paired jump points, it is more like the "island hopping" naval campaign in WWII. Each island was a very hard and expensive target, but moving between them was cheap.

  • $\begingroup$ The points have a major effect on strategy in Weber's Honor Harrington books in addition to the Starfire books. $\endgroup$ Oct 30, 2018 at 17:09

Some thoughts that come to mind, nothing comprehensive but here's what I've got:

  • Under those restraints the "border" is actually a zone roughly 60 light years across in which the government that is theoretically in control isn't actually going to want to build anything too vital in the way of arms manufacturing or other war materials, shipyards etc... and in which civilians aren't going to feel hugely safe at the best of times. In reality while there's peace, even uneasy peace, in the area the border zone will be exploited and colonised but once the balloon goes up it will quickly become a largely empty "buffer zone" as the civilians up sticks and government facilities are destroyed and aren't considered worth replacing, and/or it isn't safe to try.

  • If the jump points into systems are stable they'll be heavily mined as systems are abandoned to prevent empty star systems being exploited as stepping off points for invasion fleets. If the jump points aren't stable enough for mines then the systems will be seeded throughout with long range automated weapons with the same goal. Depending on the available technology automated weapons manufacturing may be set up to guarantee continued interdiction of particular systems, especially those that grant close access to important targets.

  • It will likely be considered worthwhile, and may actually be depending on circumstances, to put patrols into the systems that are most strategically placed as stepping off sites to raid important infrastructure.

  • In important systems, those with strategic resources and infrastructure, close to the border that remain occupied most of the available interdiction capabilities are going to be aimed at keeping a lid on the stable incoming jump points in case of a breakthrough attack and important targets are going to be heavily hardened to resist attack until help can arrive. Such systems are going to have heavy fleets on continuous patrol and rotation, and those fleets will raid back across the border where possible as well.

  • Systems without strategic resources that are close to the border are going to look more like the systems in the buffer zone as their civilian populations thin out under the threat of breakthrough attacks, this will make the border very "lumpy" as the only properly occupied systems near it are the military ones. These semi-abandoned systems are going to be quite attractive to people disaffected with the government that want to get away and set something up elsewhere.

  • Far from the border zone the war won't be a real thing to most people and as the war continues less and less military hardware is going to be evident as you get further from the border, there's not a lot of point interdicting systems that can't be directly attacked. There will still be warships but largely they'll be going from shipyards in the interior out to the border with a few smaller ships stationed in-system as much for customs interception and search and rescue work as anything else.

  • Pirates, political dissidents, separatists, smugglers, and companies who want "alternative resource channels" are going to dearly love that wide swath of abandoned and thinly patrolled space.

  • In-system operations, and the tactics thereof, are controlled more by the relative speed and maneuver capabilities of the fleets involved than by any other single factor.

Have a look at Jack Campbell's Lost Fleet, he discusses/demonstrates the limitations of in-system combat and the logistics of wars fought under similar circumstances to the Battletech system, not the same but close enough that there's some insights there that may help.

  • $\begingroup$ I love the concept of collateral chaos during a war. In a world with hundreds of populated worlds along a border but only a few key ones, while the government is prosecuting said war, all hell can break loose among the rest of the kingdom. $\endgroup$
    – user43053
    May 11, 2018 at 4:29

If you're sticking right with the system Battletech has, I think they're pretty spot on.

What would allow wars to spread significantly inside each powers territory? You have a fairly limited jump range (60 LY at best if you have Lithium Fusion batteries). Any power is going to have the Zenith and Nadir points monitored, at the least. Bigger systems will have recharge/defense stations, and defense fleets. So while you may be able to get through a few systems, with a small fleet, you're not taking the fight all the way to Tharkad without fighting in the majority of systems in between.

So what you end up with, is more of what were familiar with. Technically, the US could slip troops up well into Canada, but in small numbers. There's no solid border, its not completely secured and defended, and the majority of borders aren't. Yet when we fight on Terra, it's mostly at the borders. Sure we can get some troops behind enemy lines, but not many.


On a more tactical scale, the appropriate strategy for attacking a system would be to divide your attacking fleet(s) and come at the system from multiple axis, and at different times. Since you can jump across interstellar distances quickly but need to slog through inertial space it become easy to overwhelm defenders and get them out of position. They see an incursion and trundle the fleet to respond, but then another attacker appears in a different quadrant.

The defender needs to either move the fleet to intercept the new threat (with a consequent use of energy, reaction mass and other supplies), or dispatch the reserves. At some point either the attacker packs up and jumps out (leaving the defending fleet still near the orbit of Jupiter) or the defender runs out of resources, and a very small attacking force out of the total englobing force moves in and forces the surrender of the home planet/base.

This leads to a resource maximization strategy, where the defenders try to flood the system with as many ships or fighting platforms as possible to cover all the different approaches. This really doesn't work very well since the ships will be much smaller and less capable, and if the attacker is working the same strategy, they will be able to pump many, many more ships into the battle.

This may end up resembling fighting the Pacific theatre with swarms of PT boats rather than battleship and carrier task forces. While a task force is far more powerful, they simply cannot be everywhere at once, and given the right conditions, a swarm attack by PT boats could even be very dangerous. If the defender can arrange to lure the attacker into "restricted" space (like the Hill sphere of a planet), they may even have sufficient advantage with swarms of PT boats to defeat carrier battle groups. On the offensive, you would need to take short hops, fortify any system you manage to capture and turn its productive capabilities to expand the numbers of PT boats you have, and supporting the ability of the fleet to continue operations.

The "Grand Strategy" would then be building your industrial base, working in short "steps", building alliances to focus your resources on one enemy at a time and being able to engulf potential attackers with swarms of your own fighting platforms.


Mutual sieges abstract to the game go.

Attackers can continually introduce area denial weapons to bottle up defenders, and defenders have to sit in force right on the edge of the danger zone for fear that the next incoming is an invasion fleet instead of a bomb. If even a small attacking force breaks through the huge opportunity to maneuver becomes a big headache for defenders. Any system cut off in this way can be attacked in force eventually with more resources than it can possibly match.

Since attackers finally controlling the system allows attackers to advance, once a system is cut off from the main group it needs to be sieged by its controlling power too. Leading to 30ly buffer-zones under siege from both sides and at least a potential race to envelope larger groups where scale differences would allow eventual decisive action.


The strategy really depends on the specifics of your jump drive, and more importantly your jump points. If they are known and in "fixed" locations, then the obvious strategy is to defend the crap out of them with the equivalent of fixed defenses; minefields, fortresses, whatever is needed.

Can multiple ships come through at once? Then you're looking at beachhead battles, throwing as much as you can through a jump trying to gain a foothold in the system. If, on the other hand, only one ship (or very few) can come through at a time, then large-scale invasions become impractical against industrialized or heavily defended systems. You run into a classic mountain pass defense; it doesn't matter how big your space fleet is if they can only come through one at a time. The defenders have a huge advantage. The Grand Strategy would focus on Cold War style operations: covert actions, political influence. You either want them to voluntarily come on your side or to weaken themselves so much internally that they can't adequately defend the jump points. However, as the invader once you've got control of the jump points, now you own the system. Hell, you might not even bother with an occupation if the system is primarily meant as a waypoint to other systems. Who cares what government they're running on the planet so long as they're smart enough not to provoke you?

The overall strategy is an all-or-nothing. There's no point holding anything back, on attack or defense. You either control the jump point or you don't. There's no point keeping reserve fleet back to defend the planet. This is especially true if the jump points form a network, so there are only certain routes of getting from one system to another. The fleet at Earth isn't doing any good if the enemy has to first take Wolf 359 in order to make it to Sol; better it be out there at Wolf 359 to stop the enemy there.

If, on the other hand, jump points are limited by distance from the center of mass of the system, which is also common, but could otherwise appear anywhere, and it takes time to putter around in-system, then defensive strategy will have mobile fleets close to home. They won't stop someone from entering, because they can't defend a full sphere and distance/velocity limitations means the squadrons out at the jump sphere are going to be useless if the enemy appears on the other side. The best bet in that case is to watch them come in (because you have plenty of time) and move to intercept. In that case, you're looking at more of a World War Two style strategy from the viewpoint of the Axis: you know an amphibious invasion is coming, and given the enemy control of the seas they can pick when and where, so you sit tight and wait for them to come to you.

Of course, that works two ways: the invaders could find themselves trapped or outmaneuvered because they can't stop reinforcements from coming in behind them, or having the defenders send ships back to hit your own system.

The strategy then, would be to ensure you have reserves staying at home while you're out trying to conquer the galaxy.

So, again, it comes down the specifics of how your FTL drive works.

Also, second the recommendation for The Lost Fleet series.


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