Nor was the threat of a wormhole assault the only reason for those forts, for the twenty-three and a half hours Fearless had required to reach the Junction underscored another defensive problem. Both wormholes and stars had hyper limits, within which no ship could enter or leave hyper. For junctions, the limit was, less than a million kilometers; for a G0 star, it was twenty-two light-minutes. But any wormhole terminus and the star with which it was associated created a roughly cone-shaped volume of mutual interference, lethal to any ship passing through it, in hyper-space’s lowest bands. The danger volume wasn’t perfectly cone-shaped, and each wormhole and star created its own unique threat zone, which generally threw off spurs about the wormhole itself. Because the Manticore System was a binary, with danger volumes for each star, the Junction’s closed areas were more complicated than most, but there were always clear zones around the outer perimeter of any wormhole, gaps through which the wormhole could be approached from hyper. Which meant that while a defensive fleet stationed in orbit around Manticore or Gryphon would require a full day to reach the Junction through n-space, an assault from outside the system could (in theory, at least) drop out of hyper right on top of the Junction and already shooting.

In fact, it was less simple than that. Cutting a translation out of hyper that close was virtually impossible, so the attackers would almost certainly have to maneuver in n-space to get into attack range, which should give the forts time to detect them and, using their mobility, redeploy to meet their attack.

Yet for all their numbers, firepower, and mobility, the fortresses were too weak to stop a worst-case, multiple-transit attack by an opponent as powerful as the Havenite Navy. And that, she told herself moodily as Fearless killed the last of her speed and slid to a halt, was the real reason Manticore had annexed Basilisk in the first place.

The central nexus was the key to any wormhole junction. Ships could transit from the central nexus to any secondary terminus and from any secondary terminus to the central nexus, but they could not transit directly from one secondary terminus to another. Economically, that gave Manticore a tremendous advantage, even against someone who might control two or more of the Manticore Junction’s termini; militarily, the reverse was true.

There was an inviolable ceiling, varying somewhat from junction to junction, on the maximum tonnage which could transit a wormhole junction terminus simultaneously. In Manticore’s case, it lay in the region of two hundred million tons, which set the upper limit on any assault wave the RMN could dispatch to any single Junction terminus. Yet each use of a given terminus-to-terminus route created a “transit window”—a temporary destabilization of that route for a period proportionate to the square of the mass making transit. A single four-million-ton freighter’s transit window was a bare twenty-five seconds, but a two-hundred-million-ton assault wave would shut down its route for over seventeen hours, during which it could neither receive reinforcements nor retreat whence it had come. Which meant, of course, that if an attacker chose to use a large assault wave, he’d better be absolutely certain that wave was nasty enough to win.