I suppose that an overview is in order, I mean, it's not every day you hear of the relatively peaceful Leaf shinobi (is that an oxymoron there?) raiding villages for small amounts of plunder. Well, that used to be the case. Now? It's a lot more common, although none of them are terribly happy about it.
It's a long and not particularly happy tale, starting after Naruto's battle with Pain, Danzo's claiming the position of Hokage, and the subsequent rebuilding of Konoha.
Danzo, surprisingly, was a very good thing for the recently upset and displaced village. He made sure that the village was rebuilt quickly, including all the technological advances that Konoha had been needing for years in most of the new buildings, and made structurally unobtrusive, by that I mean that he made sure that these new advances in technology did not turn the new Konoha into a flat stone and wood industrial wasteland, he made sure that the villagers had a large part to play in the construction and design phases. This relatively innocent gesture was actually a work of political genius on his part. The villagers' input made sure that their new living conditions were exactly what they wanted down to the very basics and also pleased the civilian council members and the general public greatly, the fact that this new Hokage was coming to them for help, cooperation, and advice on things which he could easily have done by himself convinced them that, despite the bad rumours about him, he might not be such a bad thing for the village, that was the key, after the destruction of Konoha the villagers had really come together into a large group, even more of a community than they had been previously and were convinced that they would do far more for the village and each other than they had done previously.
They most definitely meant it. The non-shinobi population of Konoha threw themselves into the rebuilding wholeheartedly, erecting many buildings while the ninja, especially the hugely useful wood-user Yamato, were resting or running the many missions they needed to do to raise funds. The village was fully rebuilt within four months. And vastly improved too. Danzo had ordered massive new walls built that stretched far out into the surrounding forest leaving many acres of fresh land for farming, further building, and training. In addition to that, new bunkers far under the Hokage monument mountain had been built, with tunnels stretching far away from Konoha in case the civilian population had to flee. There were new fallback positions stocked with weapons and supplies spread throughout Konoha and the new area it encompassed in case of a lower level attack, such as was seen during the seldom talked of 'Sora' event. Danzo evidently had achieved massive influence during his days commanding Root and had amassed a huge stockpile of debts and favours that he could call in at any moment. This was shown quickly, as trade flourished as soon as the villagers were resettled. Apparently, word had spread through the world of the attack and due to some well placed rumours the 'rarity' of the native trees as Konoha timber hit an all time high as far as cost and demand were concerned, every square foot of unpaved soil in the new city of Konoha was planted with the indigenous trees and brought to maturity quickly thanks to the efforts of ninja with earth, water, and wood element affinities, turning Konoha into a literal village hidden in the leaves. Excess food, metals, and craftworks – metals, wooden objects, and the like – were also bought up as soon as they appeared. Konoha boomed, and the civilians had never been happier with their lot. They were profiting hugely, and yet prices stayed relatively low in the markets and shops due to the ready availability of resources and the newfound comradeship that the villagers enjoyed.
What of the ninja? We know that many were unhappy about Danzo before he took power, but what about afterwards? After all that he'd done for the ninja's civilian friends and relatives? The massive profits that every inhabitant was enjoying and the eradication of slum areas and poor housing meant that almost every person in Konoha was equal. Of course there would be the odd exception to that rule, but isn't that always the case, even in the most advanced civilizations? This got Danzo the support of most of the Konoha ninja, who had non-shinobi relatives or friends, and even those who had been fully against him in the first place and who were still hardcore supporters of the old Hokage, Tsunade, were forced to grudgingly admit that Danzo might not be an entirely terrible thing for the village. In fact, even Naruto was heard to say "I suppose he's not that bad.. for a mean old bastard." Which raised chuckles from his friends and more than a couple of eyebrows from Kakashi and the other teachers.
I think I digress, and some of you are probably getting bored, but stay a moment longer my friends, this long and seemingly pointless inventory of the mysterious Danzo's successes as a leader and politician has a reason. You see, this new glory and flourishing economy that had come from such a disaster would obviously attract unwanted attention from other great villages who were jealous of Konoha's accomplishment and wanted it's wealth for themselves.
That is exactly what happened.
In late winter, a year after Konoha's rebirth, Kumogakure attempted an alliance, hoping that they would benefit from the Hokage's contacts and that trade with Konoha would bring the world's attention to Kumo as well. Danzo, being the keen military mind that he was and having spent most of his life as an intelligence specialist and leading an organisation based on gathering, stockpiling, and analysing information, saw through the Raikage's front and refused their offer of alliance angering the other man greatly. The other man left Konoha without another word.
Back in Kumo the Raikage's rage was obvious. His office was located in a large rocky cavern which reverberated as he angrily threw his door closed, narrowly missing his nervously following entourage. Outside, the weather significantly darkened. Even the Raikage's favourite aide Gazani, A small man with a greasy combover who habitually wore cheap brown suits to hide his considerable prowess as a ninja, could do nothing to ease the big man's foul temper.
"Danzo. The scheming bastard. He'll pay. Oh yes, he'll pay." He roared, sending Gazani scuttling to hide beside a jutting alcove. The small man flinched as the leader turned on him, a fierce glint in his eye. "Otogakure, Gazani, that's it!" He turned to his massive oak desk and began to shuffle papers, eventually pulling out a scrap of parchment and a brush he scrawled a short message on it.
"My apologies, Raikage-sama." Simpered Gazani, as he nervously smoothed his ridiculous hair. "But I'm not sure what you're getting at."
The Raikage paused momentarily, before shooting an exasperated sigh and a swift roll of the eyes towards the cowering man. "What do you know of Otogakure, the Hidden Sound Village?"
Gazani looked slightly confused. "Orochimaru's village, what of it? I thought you agreed with Konoha that his practices were inhuman and unforgivable."
The larger man nodded. "Yes, you're right. But desperate times call for desperate measures, am I right Gazani? Would you stop cowering, man, you're a disgrace to shinobi everywhere!"
The other cringed before drawing himself to his full height and saying "These are desperate times Raikage-sama? I thought the village was doing well.. Why only last week my niece in logistics was telling me how the village's profits had increased during recent months."
The Raikage shot him a withering glare and sighed at the man's incompetence again. "The bastard Hokage has delivered a personal affront to me. Accusing me of all people of looking to leech from Konoha's glory. Pah." He spat, viciously, narrowly missing Gazani who briefly looked downwards in disgust before reverting his expression to bewildered.
"My apologies again, Raikage-sama, but I am still not following you entirely. Wasn't our plan all along to profit from Konoha's new.. ah.. desirability?"
"You know Gazani, sometimes I ask myself why I keep you as my advisor. Yes, the original plan was to somehow use Konoha to increase Kumo's income, but we didn't want anyone else to know about it, did we? No. Now that our revered Hokage has delivered a personal insult to myself and Kumo's integrity we have a valid excuse to take their wealth for ourselves.. force-full-y" He sounded out the last word slowly, pushing it through his bared teeth.
"I understand now, Raikage-sama." ("About time too" grumbled the Raikage.) "But what does the Hidden Sound have to do with this?" Queried Gazani.
"Who does Orochimaru hate more than anyone? Who would he most like to see destroyed? Who will we help him eraticate..?" The Raikage's grin was now so broad and his state of excitement so profound that Gazani could see small flickers of electricity between the large man's rear teeth.
"I see what you mean, Sir, but assuming Orochimaru takes you up on your offer will we have enough soldiers? Even with Kumo's might and the Lightening Country's standing army (which the Daimyo might not let you use) and Orochimaru's army of mutants and outcasts we might be hard pressed if our attack turns into a war of attrition."
The Raikage looked thoughtful. "I can see your point Gazani, but don't worry about the Daimyo. He's been on my payroll for as long as he's been in office. Also, I have contacts throughout the minor countries and favours from their Daimyos and other leaders that I can call in. Danzo isn't the only one with a long reach.
As a matter of fact, I know that the leader of Tanigakure, the Village Hidden in the Valley, owes me a very large debt. I think I rid him of an annoying ex-wife back when I was a genin." He smiled at the memory, but his seriousness returned swiftly. "They happen to have at least one fairly powerful ninja family in their village. I'm fairly sure I could find a use for them.
Gazani, get that message out to Orochimaru and tell me as soon as he replies."
The weedy man leapt to attention, throwing a stiff salute. "Hai, Raikage-sama."
"And not a word to anyone, mind." Warned the Raikage. "The last thing we wan is Konoha having a head start."
Gazani left shortly afterwards, leaving the big leader to write out a list of countries, men, and villages that owed him debts, and another of factions that could be bribed or coerced into collaboration. Kumo was going to unleash a storm unlike anything the world had ever seen.
Their plans went ahead quickly and, within another few months of the fateful meeting in Konoha, Kumogakure's significant shinobi force, coupled with Kaminari no Kuni's standing non-shinobi army, were camped in the Marsh Country mere miles from the border with the Valley country. There they waited while scouts and messengers skirted around the head of the Fire country spreading the word to Daimyos and ninja village leaders, calling in favours and executing politicians where necessary they gathered the forces of the many minor countries above the Fire and readied them for the attack. As expected, Orochimaru had accepted the Raikage's offer almost instantly, and had accelerated his obscene human alterations program, hoping to 'field test' his latest designs. His army was camped in secret just on the Ta no Kuni side of the Fire Country border, raring for blood.
It took a further two weeks or so to fully prepare every force for the coming fight, to draw up battle plans, gather reinforcements, and pack supply trains. The Lightening country waited patiently for word to arrive from every force signalling that they were ready to go. Kumo moved the day after the last carrier hawk arrived from the Mountain Country's leader, informing the Raikage that all was well and that they would begin their strike into the Fire country immediately.
Imagine this, dear reader. Four contingents of allied soldiers bearing down on the Fire country, the trees around them dark with the darting forms of battle ready shinobi, while Konoha sits basking in the late summer sunshine, utterly unaware of it's encroaching fate. Not a particularly pleasant thought, is it?
They did not stay unaware for long, mind you. Word of the invasion reached them very quickly, and they reacted instantly. Danzo himself oversaw the battle plans being drawn up by Shikamaru Nara and his father, the famed tacticians, fine tuning their defensive procedures and issuing orders. Hawks were dispatched to Konoha's allies in the Sand, and calls for aid were sent to the Iwagakure, the Hidden Rock village, and to Kirigakure, in the hope that these two powerful nations would react to Kumogakure's apparently unprovoked assault.
The mighty Hidden Rock village replied almost instantly, refusing to help and citing their massive losses in the last Great War and their refusal to suffer such fatalities again as their reason for not helping. Kirigakure's reply appeared in the form of their newly re-established Seven Shinobi Swordsmen and an apology from the Mizukage for not sending more forces. Danzo gladly received the seven, and despatched them quickly to reinforce the teams of Leaf shinobi that had already been sent out to counter the enemy.
Most of the invading army was made up of the regular non-shinobi soldiers that made up the country's standing ordinary armed forces and so were relatively slow on the move compared to the ninja that accompanied them. This was a great help to Konoha, as it meant that they had longer to prepare, as the enemy ninja had to stay close to their 'ground' forces to protect them against the Leaf's swift retaliation.