all about Roronoa Zoro One Piece

Even as a child, Zoro was strong enough to defeat most adults. In the anime it is shown that he was a traveler who took down dojo signs (which was something of an honor to that dojo) after defeating them. However, there was one person Zoro could not beat - the sensei's daughter, Kuina (In the anime she is the reason he joins her father's dojo in the first place. Kuina's father made a deal that if he could defeat her Zoro would take the sign. If not, Zoro have to train under him. Obviously he lost, and thus trained to defeat Kuina).

After their 2000th fight (and Kuina's 2000th victory) Zoro challenged her in private for one more match - with real swords. She beat him, and he cried with frustration, telling Kuina his dream of being the world's greatest swordsman. Hearing this, Kuina confided in Zoro, telling him that she shared the same dream but knew she could never attain it - her father had told her that girls could never be true sword masters, and that her fighting potential would decrease as her body matured. Zoro, annoyed by her defeatist attitude in spite of repeatedly winning against him, told her that one day he would beat her because he was more skilled, not just because she was a girl. The two make a promise - that either of them must become the worlds best swordsman. The next day, Kuina died falling down the stairs of her dojo.

Zoro, remembering the promise, decided to fulfill the promise for both of them, and he asked the teacher for Kuina's sword, Wadō Ichimonji, and he started to develop a new fighting style - santōryū, a three-swords-style. Before her sudden death, Zoro fought with two swords, but after her death Zoro started using her sword as well, clenched in his mouth.

Abilities
Zolo is a skilled swordsman, able to use one, two and three swords in varying attack styles, and even no swords, although he is most proficient with the fictional sword style Santōryū (literally: three sword style), clutching his third sword in his mouth. Zoro is somehow able to speak with his sword held in his mouth; Eiichiro Oda has stated that it is his heart that allows him to do so. Though not a samurai, he maintains his own code of honor. His goal is to become the greatest swordsman in the world by beating the current greatest swordsman, Hawkeye Mihawk.

Over the course of the story Zoro has used many different swords, carrying three at a time with one, the Wadō Ichimonji, remaining with him through the entire series thus far. His other notable swords are Sandai Kitetsu, Yubashiri (Yu-bashiri in the Viz translation) which he both got at a samurai sword shop in Loguetown. He recently obtained Shuusui (Autumn Water) which replaced the broken Yubashiri (which was broken by one of the Marine captains that attacked Enies Lobby). Most of Zoro's swords have been Meitou (Named Blade).

Zoro has several sword techniques at his disposal, using one sword, two swords, or all three. He is also capable of fighting effectively with no swords, and his physical strength is enough to lift a building. Zoro also has the ability to cut through solid steel, or materials as hard as steel, which he learned when fighting Das Bones (Baroque Works Mr. 1) in Arabasta. He is also capable of using the 'Asura' technique, which gives Zoro three faces and six arms, thus totaling nine swords. Including Ichibugen, the only one seen so far is Makyuusen. In addition, Zoro can expand the muscle mass of his arms, an ability he often employs to break through opponent's physical defenses.

The World's Best

Somehow he eventually learned of Mihawk, who is currently the greatest swordsman in the world. Zoro eventually went to sea looking to find and challenge Mihawk to a duel, but got lost and could not return to his home. Since fighting is more or less the only thing Zoro is really good at, he would usually take on a bounty hunter job in order to pay for sword repairs and meals. From then on, he quickly made a reputation as a "Pirate Hunter".

Because of his reputation, Zoro was offered a position and a number in Baroque Works because of his bounty hunting skills, but declined when he was not allowed to become the boss. Afterwards, he killed the person who offered, an earlier Mr. 7 of Baroque Works, for trying to kill him for refusing.

Held at the Marine Base

A moment of kindness landed Zoro in trouble with Helmeppo, the wimpy son of the Marine captain Axe-Hand Morgan. Zoro joined Monkey D. Luffy's crew after being saved from execution by the Marines, and is now one of Luffy's crew. Holding on to his dream of becoming the greatest swordsman in the world he only joined Luffy to accomplish that goal, though Luffy doesn't mind - on the contrary, he only sees it natural that the greatest swordsman and the greatest pirate are on the same crew.

Meeting Mihawk

Zoro finally got an opportunity to prove his skill when the crew came across Dracule Mihawk, who was attacking the ship of Don Krieg. The world's greatest swordsman was challenged by Zoro, but despite using his full power, Mihawk easily held him off with a six-inch knife, lamenting that he didn't bring anything smaller with him. Despite being badly wounded, Zoro continued to fight, and impressed by his courage and will power, Mihawk gave him a chance to face his Black Sword. Zoro used his strongest attack at the time, the ultimate technique of the Santouryuu, Sanzen Sekai (Three Thousand Worlds), but even so, two of his swords were shattered by Mihawk's following attack, leaving only Wadō Ichimonji. From that point on, Zoro swore never to lose to another swordsman again.

Journey onwards

Zoro has proven his skill with the sword against several powerful foes while fighting for the Straw Hats, including taking down the fish-man Hatchan, and defeating an entire town of Baroque Works agents at Whiskey Peak. He even defeated Das Bones, the powerful assassin in Baroque Works. After Baroque Works was defeated in Arabasta, he was given a bounty of 60,000,000 belie.

He continued to travel with the Straw Hats to Skypiea, defeating Ohm, one of Eneru's underlings. With the defeat of Eneru, Zoro and the Straw Hats returned to the Grand Line.