Short answers, pulled from the story.
The word samurai derives from the verb saburau, meaning one who serves. In the early Kamakura period, the bakufu explicitly prohibited those of bonge status from carrying weapons within city limits, ensuring that archery, swordsmanship, and horsemanship remained the exclusive attributes of the bushi class.
Samurai became conspicuously involved in reclaiming land from the wilderness to feed a growing population, emerging as a landowning class by the 11th and 12th centuries. The imperial court began dismantling the national conscript army system by 792 AD, leaving security in the hands of local magnates who had the resources to train professional mounted archers.
The Minamoto clan defeated the Taira clan in the Gempei War of 1180 to 1185 to establish the first shogunate. In April 1185, the controversial child emperor was drowned by his own grandmother, and the new emperor, Emperor Go-Toba, was of Fujiwara lineage on his mother's side.
When matchlocks were introduced from Portugal in 1543, Japanese swordsmiths immediately began to improve and mass-produce them, and by the end of the Sengoku Period, there were hundreds of thousands of arquebuses in Japan. The bow fell into disuse and was replaced by the katana, which could be held short, and the short, light naginata, which appeared in the Nanboku-cho period and gradually became more common.
In 1876, the government forbade anyone outside the military to wear swords even if they were of samurai lineage, and repealed the right of a samurai to strike an insolent commoner with potentially lethal force, known as kiri-sute gomen. In 1947, the shizoku class was abolished, marking the final end of the samurai as a legal entity.