By the order of Onoki, all members of the first and third explosion corps division along with hundreds of regular Iwa shinobi are sent out to completely eliminate Uzushiogakure with aid of Kumo and Kiri shinobi.
Total Iwa force which would be invading Uzushiogakure was around 1000 (including explosion corps).
Onoki and other Kages learned their lesson from the first great ninja war. Although Konoha lost it's leader second Hokage during the first ninja war, they still won the war.
How? you ask?
It's because of Uzushiogakure helped Konoha. Uzushiogakure had close ties with Konoha, due to them being distant blood relatives with Konoha's Senju can.
(A/N: I don't know who won first great ninja war, so I just decided that Konoha won)
Although Uzushiogakure was small, their power is rivalled great ninja villages due to their renowned fuinjutsu.
After the first great ninja war, Konoha has risen up to power with aid of Uzushiogakure, faster than any other villages.
Onoki and other kages were very worried about this Uzushiogakure.
Konoha itself was already strong enough, but with the aid of Uzushiogakure, the balance between five great villages will ruin.
Therefore they decided to destroy Uzushiogakure with combined power once for all.
All the members of explosion corps got tense since if we attack Uzushiogakure, they were sure this would bring domino effect and cause another ninja war.
Goro (head of the explosion corps) naturally was the leader of our invasion force.
We were to meet Kumo and Kiri shinobi at the border between Kumo and Uzushiogakure.
Our Iwa force moved at a fast pace.
Since it was inevitable to hide the movement of huge shinobi force going towards Uzushiogakure, we decided to move as fast as we can.
Also, in order to give a surprise invasion, three allied villages made set up.
Set up was like this: Iwa and Kiri mobilized the army to attack each other to avenge their previous kages.
They would fight at the border of Kumo and Uzushiogakure.
Kumo mobilized their own army under the pretext of stopping this battle since two sides are fighting in Kumo land.
In summary, Iwa and Kiri fight each other while Kumo comes in to stop the fight.
Although it wasn't a perfect plan, it was a good one.
If I have to guess who came up with this plan out of 3 kages, I will pick Onoki or Third Raikage.
The third Mizukage looks calm and smart on surface, but if I consider his actions such as Kiri bloody graduation ritual or planting third tailed beast inside unknown Konoha shinobi (Rin) to destroy Konoha inside? It makes me presume that he is not very skilled at strategy.
I remember the third Raikage mentioning the second Hokage as if he was in the same generation with the second Hokage when he got resurrected in the fourth great ninja war.
That proofs he was still Raikage during the First ninja war.
This also meant while other village kages died during the first ninja war, only third Raikage survived.
I don't believe he survived that bloody first great ninja war just with strength. I am sure he is good at planning too.
Therefore, there is a chance he planned this scheme.
Onoki is very crafty in politics and diplomacy and strategizing.
This made me respect Onoki.
Although his teaching is not excellent, his intelligence is certainly at a high level.
The only reason Iwa lost to Konoha every ninja war is because they lack talented shinobi compared to Konoha.
Onoki might have planned this scheme instead of third Raikage.
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Our forces have arrived at the meeting location after marching for 4 days straight.
Kiri forces were already there, waiting for us and Kumo forces.
It seems Kiri is also serious about eliminating Uzushiogakure. Their forces seemed to be as big as our Iwa forces.
Most importantly, all seven great ninja swordsmen were in the force.
Although both sides are allied with each other to attack Uzushiogakure, it doesn't mean that they trust each other.
One day later, Kumo force arrived too. They were also settled camp 1km apart from Iwa and Kiri.
Kumo forces were around 700 shinobi.
Although Kumo's force was less than Iwa or Kiri, Kumo sent almost every storm corps members.
I was really fascinated by these lineups.
Approximately 2700 shinobi force including Explosion corps, Seven ninja swordsmen, and Storm corps would invade Uzushiogakure.
No wonder why, it became ruins in one day!!!
Later, 10 representatives from each side gathered around to discuss when to attack, who would initiate the attack, etc.
Although I was not there, I bet tension was immeasurably high.
All representatives returned to their respective camps to prepare to perform according to the battle plan.
Goro-san was one of our Iwa force representatives. He came back from the meeting and told us about a battle plan.
Battleplan was like this: Iwa explosion corps act first.
We use our explosion power to destroy the barrier surrounding Uzushiogakure, important buildings such as weapon warehouse and shinobi Barack to confuse Uzushiogakure shinobi.
Then, Kiri forces use the all combined water styles to flood Uzushiogakure.
This would make shinobi from Uzushiogakure to prioritize saving civilians instead of fighting back.
Next, Kumo force with their fast speed (due to their lighting attribute) to break in and kill most of the high-ranking Uzushiogakure shinobi.
Lastly, Iwa and Kiri forces join the battle and eliminate Uzushiogakure shinobi.
The Invasion was decided to commence at 10 pm.
Kiri, Kumo, and Iwa forces arrived Uzushiogakure at 9;45 pm and got into their battle positions immediately.
All of our explosion corps members surrounded Uzushiogakure and waited for the signal.
Uzushiogakure gatekeepers were not idiots.
They heard huge numbers of footsteps coming towards them.
They were worried and reported to their sensor shinobi.
Uzushiogakure sensor shinobis were very shocked when they scanned through around the villages.
Around 2700 shinobi forces were surrounding Uzushiogakure!!!!!
As soon as they were about to report to their higher-ups, they heard a bright signal lighted up.
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At exactly 10 pm, the signal was fired and all of our explosion corps members used their explosion release at the same time.
I also used Earth style: Pistol Gun jutsu and exploded them at the barrier.
BOOOOOOOOOMMMMMMMMM!!!!!!!!!!!!!!!!!!!!!!!
No matter how sturdy the barrier was, it couldn't hold our combined explosion powers and has fallen.
All Uzushiogakure shinobi and civilians were shocked by the loud explosion and panicked.
After the barrier was collapsed, the Kiri force didn't wait any longer and used all of their water styles to flood Uzushiogakure.
As we expected, most of the active Uzushiogakure shinobi didn't counter back, instead, they were busy saving civilians as much as they could from the flood.
Finally, Kumo force broke in and started to massacre Uzushiogakure shinobi.
Soon our Iwa force and Kiri force joined them and started to destroy Uzushiogakure.
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Me, Gari, and other 3 explosion corps members are tasked to destroy weapon warehouse and try to steal fuinjutsu related to explosion tag as much as we could.
I killed a few Genins so far.
They all just got emotionalized seeing their village getting crushed, messing up their fighting form which led to their death.
All of our explosion corps members were used to killing prisoners, therefore we didn't feel anything.
I will admit I felt a bit bad for killing them. But that was it. These are all what ninjas do in war or battle, as we kill each other.
We have so far successfully destroyed 3 weapon warehouses.
Suddenly I saw flying chains passing through me at incredible speed. Chains then pierced 3 of our explosion members instantly.
'What?? What just passed through me?
Those chains!!!!
Don't tell me those chains are hidden jutsu: Adamantine sealing chain???'
Then another wave of chains was coming at me and Gari.
We both used Shunshin (body flicker) to evade the chains.
We looked at the attacker. He was a jounin uniform of Uzushiogakure and very tall with bright red hair color.
I didn't need to see his face to know that he was very angry.
'Alright, He is the enemy's jounin who can use one of deadly Uzushiogakure's hidden jutsu: Adamantine sealing chains.
I am DEFINITELY sure he is one of the strongest Jounin in Uzushiogakure.
Why is he here, shouldn't he be saving civilians instead of fighting? '
"HOW DARE YOU SHITS ATTACK OUR SACRED VILLAGE AND KILL EVERYONE INCLUDING MY SON!!!!
I WILL KILL YOU ALL.
I WILL AVENGE MY SON!!"
'Okay, it seems like one of the genins I killed was the son of this guy. Just how bad is my luck to face this monster this soon after entering Uzushiogakure?'
There was 0 % that he will let us go. Our only option is to fight back.
There was no way I can beat this guy alone. Gari also thought the same as me.
We decided to cooperate and defeat him.