When the Arduans first came they arrived in enormous groups containing millions of individuals. These two fleets threatened the PanSentient Union and required the entire combined forces of all the allied races two years to eventually defeat. And then the limited victory was only made possible by internal division among the Arduans. In the end a portion agreed to an arimistice and the rest took their fleet and fled. That was with two groups.
Now 12 more groups have arrived. Joined with the original Arduans who would not make peace they set out to wipe the galaxy free of the annoying nonArduans. With the size of their fleets and the intelligence gained from the earlier arriving Arduans they cause unprecedented destruction. Not just to PanUnion fleets, destruction far beyond anything previously imagined.
The Union people fight back, hold off the advance for a while, come up with some stratagems. Then the Arduans reveal their secret weapon, and an old foe comes to visit. Looks bad for the hoomans, probably they'll be exterminated.
Another fine war porn piece. Lots of battles seen from the strategy room, some actual combat scenes, and a lot of planning and plotting and espionage. There is a good deal of time spent on the war front, but the main focus of the book is the stealthy maneuverings of a group trying to decipher the enemy plans. Many tech upgrades and a ramping up of the destruction far surpassing the previous novels in the series. One weapon in particular has an obvious use that is not exploited, so even this massive level of destruction could be surpassed in the future.
If you like war porn this is possibly the best series you will find anywhere.