“The Achuultani possess no means of interstellar FTL communication other than by ship. How they could’ve been around this long and not developed one is beyond me, but they haven’t, which means that once a ‘great visit’ is launched, they don’t expect to hear anything from it until it gets back.”
“That’s good news, anyway,” Hatcher agreed.
“Yes, it is. Especially in light of some of their other limitations. Their best n-space speed is twenty-eight percent of light-speed, and they use only the lower, slower hyper bands—again, we don’t understand why, but let’s be grateful—which limits their best supralight speed to forty-eight lights; seven percent of what Dahak can turn out, six percent of what the Guard can turn out under Enchanach Drive, and two percent of what it can turn out in hyper. That means they take a long time to complete an incursion. Of course, unlike Enchanach Drive, there’s a time dilation effect in hyper, and the lower your band, the greater the dilation, which means their voyages take a lot less time subjectively, but Brashieel’s ship had already come something like fourteen thousand light-years to reach Sol. So if the incursion sent a courier home tomorrow, he’d take just under three centuries to get there. Which means, ladies and gentlemen, that if we stop them, we’ve got almost six hundred years before a new ‘great visit’ can get back here. And that we know where to go looking for them in the meantime.”
A soft growl came from the assembled officers as they visualized what they could do with five or six centuries to work with.
“I’m glad to hear that, Hector,” Hatcher said carefully, “but it leaves us with the little matter of three million or so ships coming at us right now.”
“True,” Colin said, waving MacMahan back down. “But we’ve learned a little—less than we’d like, but a little—about their strategic doctrine.
“First, we have a bit more time than we’d thought. The incursion is divided into three major groups: two main formations and a host of sub-formations of scouts which do most of the killing. The larger formations are mainly to back up the scout forces, each of which operates on a different axis of advance. Aside from the one which already hit us, they’re unlikely to hit anything but dead planets as far as we’re concerned, and a half-dozen crewed Asgerds could deal with any of them. If we can stop the main incursion, we’ll have plenty of time to hunt them down and pick them off.
“The real bad news is coming at us in two parts. The first—what I think of as the ‘vanguard’—is about one and a quarter million ships, advancing fairly slowly from rendezvous to rendezvous in n-space to permit scouts to send back couriers to report. We may assume one’s already been dispatched from Sol, but it can’t pass its message until the vanguard drops out of hyper at the rendezvous, thirty-six Achuultani light-years from Sol. Given the difference in length between our years and theirs, that’s about forty-six-point-eight of our light-years. The vanguard won’t reach their rendezvous for another three months; we can be there in about three and a half weeks with Dahak, and a hell of a lot less than that for the Guard in hyper.
“And take on a million ships when you get there?” Hatcher said.
“Tough odds, but I’ve got a mousetrap planned that should take them out. Unfortunately, it’ll only work once.
“That’s our problem. Even if we zap the vanguard, that still leaves what I think of as the ‘main body’: almost as numerous and with some really big mothers, under their supreme commander, a Great Lord Tharno.
“Now, the vanguard and main body actually keep changing relative position—they ‘leapfrog’ as they advance—and their rendezvous are much more tightly spaced than the scouts’ are. Again, this is to allow for communication; the scouts can’t pass messages laterally, and they only send one back to the closest main fleet rendezvous if they hit trouble, but the leading main formation sends couriers back to the trailing formation at each stop. If there’s really bad news, the lead force calls the trailer forward to link up, but only after investigating to be sure they need help, since it plays hell with their schedules. In any case, however, at least one courier is always sent back and there’s a minimum interval of about five months before the trailer can come up. With me so far?”
There were nods, and he smiled grimly.
“All right, that’s our major strategic advantage: their coordination stinks. Because they use hyper drives, their ships have to stay in hyper once they go into it until they reach their destination. And because their maximum fold-space com range is barely a light-year, the rear components of their fleet always jump to the origin point of the last message from the lead formation. Even in emergencies, the follow-on echelon has to jump to to almost exactly the same point, assuming they mean to coordinate with the leaders, because with their miserable communications they can’t find each other if they don’t.”
“Which means,” Marshal Tsien said thoughtfully, “that your own ships may be able to ambush their formations as they emerge from hyper.”
“Exactly, Marshal. What we hope to do is mousetrap the vanguard and wipe it out; I think we’ll get away with that, but we don’t know where the rendezvous point before this one is. That means we can’t stop the vanguard’s couriers from telling Lord Tharno about our trap, meaning that the main body will be alerted and ready when it comes out.
“So we probably will have to fight the main body. That pits seventy-eight of us against one-point-two million of them: about fifteen thousand to one.”
Someone swallowed audibly, and Colin smiled that grim smile again.
“I think we can take them. We may lose a lot of ships, but we ought to be able to swing it if they pop into n-space where we expect them.”
A long silence dragged out. Marshal Tsien broke it at length.
“Forgive me, but I do not see how you can do it.”
“I’m not certain we can, Marshal,” Colin said frankly. “I am certain that we have a chance, and that we can destroy at least half and more probably two-thirds of their force. If that’s all we accomplish, we may not save Earth, but we will save Birhat and the refugees headed there. That, Marshal Tsien—” he met the huge man’s eyes “—is why I’m so relieved to know we’re sending one of our best people to take over Bia’s defenses.”
“I am honored by your confidence, Your Majesty, yet I fear you have set yourself an impossible task. You have only fifteen partially-manned warships—sixteen counting Dahak.”
“But Dahak is our ace in the hole. Unlike the rest of us, he can fight all of our unmanned ships with full efficiency as long as he’s in fold-space range of them.”
“And if something happens to him, Your Majesty?” Tsien asked quietly.
“Then, Marshal Tsien,” Colin said just as quietly, “I hope to hell you have Bia in shape by the time the incursion gets there.”
Chapter Twenty
“Hyper wake coming in from Sol, ma’am.”
Adrienne Robbins, Lady Nergal (and it still felt weird to be a noble of an empire which had died forty-five thousand years ago), nodded and watched Herdan’s holographic projection. The F5 star Terran astronomers knew as Zeta Trianguli Australis was a diamond chip five light-years astern, and the blood-red hyper trace indicator flashed almost on a line with it.
Adrienne’s stupendous command floated with three other starships, yet alone and lonely. The four of them were deployed to cover almost a cubic light-year of space, and Tamman’s Royal Birhat was already moving to intercept. Well, that was all right; she’d killed enough Achuultani at the Siege of Earth.