Short answers, pulled from the story.
Samurai became conspicuously involved in land reclamation and emerged as a class of landed lords during the eleventh and twelfth centuries. This development occurred after the imperial court issued an edict ending most conscription in 792, which allowed professional mounted archers from wealthy families to replace peasant conscripts.
Minamoto no Yoritomo established the first shogunate by creating a parallel military government in Kamakura between 1180 and 1185 following his victory in the Gempei War. He promised lands and administrative rights to warriors who swore allegiance to him, thereby founding the institution that would define Japanese feudal governance for centuries.
The introduction of matchlocks from Portugal in 1543 caused traditional samurai warfare tactics to decline because infantrymen called ashigaru began fighting in close formation using spears and guns. Traditional weapons like bows and heavy armor fell into disuse as they were difficult to maneuver compared to firearms requiring only weeks of training to master.
Samurai became a truly hereditary class and lost their military function after the Battle of Sekigahara in 1600 and the subsequent siege of Osaka in 1615 which initiated two hundred fifty years of peace. During this era most samurai moved from land to castle towns where one town existed in each domain and gradually transformed into aristocratic bureaucrats under Neo-Confucian influence.
The shizoku class was finally abolished in 1947 following decades of reforms that stripped samurai of their privileges between 1873 and 1879. These changes included taxing stipends, transforming them into interest-bearing government bonds, and forbidding anyone outside the military to wear swords in 1876.