Time for the big battle...

OPERATION THORS HAMMER:Silver sabre.
The massive pegacorn flew into the chaos that had engufled Canterlot,behind him over two thousand dragons,ponies and other creautes followed him as they smashed into the remains of Celestias army. His wings were fully spread out like the angel of death itself.
"This is Silver sabre to all UEA units,good hunting".His final battle orders were transmiited by radio for the last time before he dived into the battle itself.

All over the huge city,buildings collasped as dragons smashed into them,Earth ponies of the UEA knocked down walls,allowing Unicorns to destroy hundreads of royal guards with thier deadly magic. The Pegasus ponies of the last four remaining strike divisions engaged in a massive fight for air supremecy above Canterlot itself.

All over,hundreads died every minute as the Royal guard blew up bridges and towers,intending to stop Silver sabres forces process.
The commander of the UEA then spotted a battalion of fresh guards approaching his already overstreched forces,gritting his teeth the Pegacorns attack was fast and furious as he flew at house level and unleashed his magic on the battalion,many of them were stunned,the others just collasped unconciously.

"Good job,maybe I should lose my job and go back to a strike commander".He commented on handiwork,pleased with it as he hadnt killed any,infact none of the civillian deaths were due to his own forces!.It was the guard that was killing thier own. Celestia had really outdone herself with recruiting psychopaths for her beloved private was,Silver sabres forces had already encircled and crushed any resistance left in the majoirty of Canterlot.

The capital of Equestrias defences had been cracked wide open and already,just three hours into the battle it was clear who had won this fight.
"Celestia just do the right thing and surrender".The gigantic pegacorn mumbeled to himself. All of a sudden his ear piece began to flash,it was one of his subordinate commanders stating a report.
"Report"
"Sir we have conquered the majoirty of Canterlot,most of the civilains are safe and the remanining members of the guard are being transferred so we can check about war crimes,however Princess Celestia has bunkered down in the great hall,she has the elements of harmony in there along with a regiment of the royal guards and a bunch of other ponies".The subordinate commander reported in and Silver sabre felt his blood run cold,Celestia was going to take everypony down with her.

"I suppose I better stop her".He said to himself before heading for the great hall at top speed.

Great hall:Celestia,Luna,Twilight,Fluttershy,Rarity,Pinkie pie,Applejack,Rainbow dash,Shining armour,Cadence.

"Get the elements ready Luna,set to full power,all guards left DEFEND ME!".
"Yes princess".

Twilight couldnt believe it,Celestia had gone was powering up the elements,intending to kill everything in couldnt she just give up?,cleary Luna looked terrified.

"BBBFF?"
"Yes?".Shining armour,conforting his wife came over.
"Can you stop her?".Twilight asked,concerned that her brother could stop the princess. He looked sad and replied thoughtfully."No,she is too powerful...I think too powerful for her sister".He answered in the knowledge that they would all die.
"What about Silver sabre,Raritys brother?".Twilight asked,even though he was the enemy now.
"My brother could defeat anypony!".Rarity shouted,defending the slight she felt that Shining armour could say.
"I dont think he could,he is powerful but defeating Celestia?..that would require a unnatural type of energy and concentration...but moving the subject before we all die..hasnt anypony noticed that Luna acted kind of strange when Silver sabre used to be around,I mean even the mention of his name causes her to go quiet...do you think she...".

"Has the hots for my brother?,come on,this is my brother we are on about haha...are you serious?".Rarity joked then realised that what the guard could be saying was Luna really liked the stallion,but in doing so...she wouldnt be able to use the elements to kill him.

"Fire away Luna!".They all heard Celestia,in a manic voice shout. She had won,she was going to kill them all,the giant rainbow lit up the sky and Lunas face became visable,she REALLY didnt want to do it,and then her side of the spell Celestia turned on her sister.
"You are weak Luna,why I even bothered to keep you is unkown to me".She laughed,then twitched before sending a hurtful spell at Luna.

"No,you are the weak one".The roof the great hell blew upon and a mighty stallion with gigantic wings and a horn that rivalled Celestias descended from guards tried to stop him but Silver sabre merly froze them into ice.

BOSS FIGHT!.
Celestia looked at her former military commander and eyes lit up and she instantly dropped her spell on Luna and ran at the stallion.
Silver sabre merley did the same and the two locked horns. "Your time has come Celestia,give up now".He spoke camly even as the princess tried to break his did the same trying to break her horn.

The two powerful alicorns then broke off before entering a duel with each other for control of the world. Celestias blue magic vs Silver sabres red and black magic,the ground shook around them and came apart as the two mighty beings tried to gain the upper advantage. Every little bit of mental power was poured into the fight.

At first Celestia gained the advantage,her experience and knowledge of spells gained her the early push,but then like in all of her wars she tried to push too soon and her opponent siezed on her lack of breakable power.
Silver sabre in return turned off the mental stability and started to do his legendary Excalibur spell to full power and it gave him the heavy weight needed to Celestia was being pushed back until the sheer power of her horn was the only thing left from her hated military commander winning.
"Dammit,wait...he is using his mental powers to win,if I can turn that into instability...".She spoke to herself,turning her defense into a spell aimed at Silver sabres powerful spell entered the stallions mind and instantly the effects was seen as he began to sweat heavily and began to bleed from the inside again.

Thats when his mental prowess began to collaspe and his spell went into overdrive...then it sabre lost the battle. His mind overloaded and a burning feeling erupting,to all intents and to the horror of both Luna and Rarity,he collasped.

Luna+Rarity.
The two ponys ran up to the defeated stallion and looked at each other.
"We are going to have to fight Celestia...for Silver sabre!".Luna and Rarity said together. Combining thier powers into one bright lance of magic in order to defeat Celestia.

"Im just getting started!".The now mad tinpot headed Celestia crackeled,using her power gained from the battle to match the twos energy in another duel.
The two ponys strained as they tried to keep the balance of power in thier soon it became ovbious that Celestia was too powerful for even a 2vs1 duel.
"I cant take it!".Luna shrieked,the guilt of killing so many and dueling her sister was too much...soon just like Silver sabre she collasped and became unconcious.
That left Rarity to handle the duel on her own,pulling out the anger of her brother to help her,the unicorn manged to keep the power balance steady until Celestias power was too much.

"Anyone else...dont think so!".Celestia screamed triuphently as she defeated Rarity,Luna and SIlver sabre in less than five minutes. Her power was now absolute. She aimed her beam and combined it with the elements of harmony to recreate the powers that had killed so many millions.

The princess then began to aim it at Luna and Rarity,as they were on the floor together."Goodbye my little ponies".Celestia crackeled and the beam of death began to fail?. "What the...".She said confused as the elements of harmony didnt do anything.

Then she realised that Silver sabre wasnt on the ground anymore,she began to look around horrified that he had escaped somehow.

"Dont even think about harming my sister!".A massive punch knocked her out."Or Luna,shes cute".