Battle music: Unbreakable by Sabaton.
(This is the best I could find, although not the best for this chapter. If someone knows of anything better, let me know.)

Less than a month later, and the steam-roller was closing in on Chrysalis. After securing Baltimare and having Griffonian ships delivering supplies to them, they moved out, using the shorter supply lines to move faster. With them, in addition to food, spare cloaks, and other bits of supplies, they also brought news from the northern front. While much smaller, the Crystal Empire, the Griffons, and the Yaks all had secured a few of the northern Equestrian cities, like Stalliongrad and Trottingham. They were, slowly but surely, making their ways south. A majority of Changelings had been redirected north to deal with them as they were technically closer to Canterlot.

The southern front, had now split into two groups. Army group Alpha, mostly the Saddle Arabians, the Buffalo, the Dragons, and half of the Night Guard would skim along the coast, heading north to secure Manehattan. Army group Omega, the Griffonains, the Pryhans, the rest of the Night and the Royal guards, would head for Canterlot to cut off the head of the snake. That left her Command, Army group Omega, with two options for getting to it: Follow the roads around the Canterhorn mountain range, or cut through the Everfree forest and come up from the valley. After much debate, they decided to cut through the forest, despite the risks.

Outside the forest, Rainbow gazed into it as the Army group got ready to move. The dark, ominous woods looked, after seeing pre-unification wars Demosian woods, looked no different, and as such, no less dangerous. Of course, she knew about the things in there that weren't in Demosian woods: Manticores, Cockatrices, Hydras, and other creatures. Vexillum came up next to her, saluting and said, "Ave, Praetor. The Pedes are ready to move, even the tin cans."

"Excellent", she said. "Get all of them ready to move. Wonderbolts and Griffonians in the air, everyone else stick on the road. Royal Guards in front; I want to keep an eye on them. No trumpets, no singing, stay on the trail. And, for the sake of the Empire and Damocles, don't touch ANYTHING blue."

While the lack of trumpets weren't playing, it was likely the marching could be heard from Canterlot. Princess Luna had a route they would be taking that was rather unknown, however; an old, Pre-Nightmare moon road. It cut through the heart of the forest, but it was supposedly abandoned even before Lunas banishment, so it was likely unknown to the Changelings.

She was at the head of the column, with the Royal guards behind her. Behind them would be the Pryhans, with the Night Guards bringing up the rear and the fliers over them, just above the canopy. Unfortunately, a group of ponies who she didn't want to talk to also made their way to the front, and were also giving her a tirade, much to her ire.

"Why did you do it?", Fluttershy said, eyes narrowed. She was likely trying to do her 'Stare', but it came off as more adorable than anything.

"Because", she said, growing annoyed. "He left his post, and put the entire campaign at risk. What was I supposed to do? Let him get away with it? No; it sets a bad precedent, and he'd likely try to do something similar in the future. It was the same with Brigands and Raiders back home, it's the same with him here."

Rarity said, "But, darling. Did you have to be so, barbaric, about it. I mean, you gave poor Twilights brother scars, and scars never look good on anypony." She then realized what she said when Rainbow looked at her, eye half-lidded. "Er, no offense, darling."

"Listen, just-you hear something?", she said, ears rotating. She came to a halt and raised a talon, grinding the column to a halt.

"Ah don't here anything", AJ said. "Y'all sure you ain't goin' mad as a kitten locked in a clear box in a room full a' yarn?"

Rainbow kept her talon up, walking forward a bit. She had heard a faint whooshing noise, coming from the bushes a short ways in front of her. She took off to hover a few feet in the air, drawing a crossbow pistol as she got closer. It could've been a bunny; or it could've been a Timberwolf. As she got close, she saw a rustle in the bushes, and fired a bolt.

A cry of pain went out; definably not an animal. A changeling spilled out of the bush, the bolt imbedded squarely in his forehead, by his horn. Her ears swiveled again, registering more noises. Her eyes scanned the bushes, and she saw more wrestling. She then caught on with what was going on: "AMBUSH!"

As if on que, Changelings emerged from the sides of the trail, letting out battlecries of clicking and hissing. Vexillum began shouting orders to the Royal Guards using his rune to translate his orders, and she drew one of her swords to fight up close.

She swung at the nearest one, cleaving through his hoof when he tried to block. He screamed, and she pulled it out and slashed his face. She then sheathed her crossbow and drew her other sword, head for the other bugs near the front of the column.

To her surprise, she saw the traitors actually fighting back; she honestly expected them to run away as soon as the one she shot fell out of the bush. Instead, each* fought back in their own way. Pinkie had pulled out her party canon from nowhere, firing at them and sending groups of them back into the bushes, covered in frosting. AJ, obviously, was bucking them away, which, while the bugs didn't die, looked rather painful. Twilight, also obviously, fired bolts of lavender magic from her horn, blasting many of the bugs back or rendering them unconscious. Fluttershy and Rarity, however; they WERE cowering behind Vexillum, who just rolled his eyes and held his shield a little bit closer to himself.

The Royal Guards also were surprisingly effective in fighting back. Vexillum must've been doing well in instilling some discipline and some more basic fighting skill, as they organized, rallying behind their lieutenants and Shining Armor (Who, while he had lost his command, was still a respected figure in the guard.) They then, displaying a bit of tactical finesse, began to go for a divide and conquer strategy, splitting apart larger groups and beating the smaller ones.

Soon, through a mix of these factors, the bugs were driven back surprisingly quickly. Rainbow, marveling at the frankly stunning victory over the Changelings by the Guard, was taken by surprise when Princess Luna arrived next to her. "A group appeared on you side as well?"

"Yeah!", she said, turning to the alicorn while the survivors fled into the woods. "How in the name of the Empire did they find this path? I thought you said it was abandoned before you went all 'Nightmare Moon'."

"I did, and it was. I don't know how they could've found it", she said.

Twilight stepped forward, saying, "Maybe some ponies from Ponyville or Canterlot escaped and fled into the Everfree. The Changelings could have found it while looking for them, and sent those drones over here when scouts or something saw us moving over on the other side of the forest. The road for going around it goes north at least twenty miles ago."

They considered it, and Luna said, "It is the best theory we have."

"Aye", Rainbow said. "Although we should still keep an eye open. If these bugs were as good at infiltration as you say, then they could've already done it. Until then, we can't afford to slow down based on nothing but theories. Get the troops reorganized, and prepare to move out."