Could a commoner become a samurai?

In the Sengoku period, yes — military skill and loyal service could earn promotion. Toyotomi Hideyoshi himself began as a peasant's son (or low-ranking farmer-soldier) and rose to become the most powerful man in Japan. His chief generals included men of humble origin. After Hideyoshi issued his class separation edicts (1591) and the Tokugawa institutionalised the class system, the answer became effectively no — with rare exceptions like being adopted into a samurai family.

Could samurai status be lost?

Yes. A samurai whose lord was defeated or destroyed became a ronin — a samurai without a lord. If a ronin could not find new employment, he might be forced to take up farming or trade, effectively leaving the samurai class in practice if not legally. Serious crimes could result in formal disenfranchisement. The Meiji government abolished samurai status entirely in the 1870s-80s.

How did samurai status work in the Edo period?

In the Edo period, samurai status was rigidly hereditary. You were samurai because your father was samurai. The class was legally defined, with specific rights (the right to wear two swords, to have a family name) and obligations (service to one's lord). Rank within the samurai class was also hereditary — a low-ranking retainer's son would begin at a low rank, regardless of personal ability. Merit could affect assignment but rarely changed formal status.

How Did Someone Become a Samurai?

The simple answer: by being born into a samurai family. For most of the samurai era — and rigidly by the Edo period — samurai status was inherited, not earned.

The more interesting answer involves who was allowed to become samurai, when the rules changed, and why Japan’s most powerful man worked hard to ensure no one could follow the path he had taken.

The Hereditary System

From the formation of the samurai class in the Heian and Kamakura periods, warrior status was substantially tied to family lineage. Lords recruited retainers from established warrior families; those families’ sons became warriors in turn. [history]

By the Edo period, this was legally rigid. The Tokugawa system defined four main social classes: samurai, farmers, artisans, and merchants (shi-nō-kō-shō). Samurai status was hereditary. You could not earn your way into the samurai class through personal merit alone. A blacksmith’s son was a blacksmith; a samurai’s son was a samurai, whatever their individual talents. [history]

Rights came with the status: samurai alone could wear two swords in public, carry a family surname, and claim the obligation of a lord’s service. These markers were visible and legally protected.

The Sengoku Exception

The Sengoku period was different. A century of near-continuous civil war created opportunities for men of ability regardless of origin. Lords desperately needed capable commanders and rewarded results. Men of low birth who demonstrated military skill, strategic ability, and loyalty could be promoted to samurai status and beyond. [history]

The most extreme example is Toyotomi Hideyoshi — born, depending on the source, as a peasant’s son or a low-ranking soldier’s son in Owari province. He entered Oda Nobunaga’s service as a sandal-bearer. By the time of Nobunaga’s death in 1582, Hideyoshi was one of his chief generals. By 1590, he was the supreme power in Japan. [history]

The Door Closes

Having risen from the bottom himself, Hideyoshi moved to ensure no one could do the same. His 1591 edicts separated the classes formally:

The Sword Hunt (katanagari) (1588): Farmers were required to surrender weapons. Only samurai could bear arms.
Class separation orders (1591): Farmers were registered to their land; samurai were registered as warriors. Movement between classes became legally prohibited.

The logic was partly practical (a disarmed peasantry was easier to govern) and partly political (Hideyoshi’s unprecedented rise was an anomaly he did not want repeated). By registering people to fixed social roles, he prevented the social fluidity that had produced him from producing rivals. [history]

The Tokugawa shogunate inherited and reinforced this system, maintaining the class structure until the Meiji Restoration.

The End of Samurai Status

The Meiji government abolished the samurai class progressively between 1869 and 1876. Former samurai were given government bonds as compensation, stripped of their monopoly on sword-wearing, and prohibited from wearing swords in public (1876). The class that had defined Japanese society for seven centuries ceased to exist as a legal category within a generation.