Short answers, pulled from the story.
Buddhism arrived in Korea in 372 CE when the monk Sundo brought texts and statues to the court of King Sosurim in Goguryeo. This event marked the beginning of Buddhist influence on the Korean peninsula after centuries of shamanism dominating local beliefs.
Tongbulgyo or interpenetrated Buddhism is a holistic approach that resolved inconsistencies within foreign Buddhist traditions by emphasizing unity and interrelatedness. Wonhyo, a prominent scholar-monk from the Unified Silla period, exemplified this effort when he abandoned his journey to China after realizing enlightenment depended on the mind rather than geography.
Monks established nine mountain monasteries known as gusan, each representing different lineages during the latter Silla period. Jinul later reformed these practices by introducing the hwadu method at Songgwangsa monastery on Mount Jogye, which remains central to Seon practice today.
The first woodblock edition of the Tripiñaka called Tripitaka Koreana was produced between 1210 CE and 1259 CE during the Goryeo Dynasty. The second surviving edition resides at Haeinsa temple in Gyeongsang after the first was destroyed during a Mongol attack in 1232.
Buddhist monks organized guerrilla units between 1592 and 1598 to repel Japanese invasions under the leadership of Seosan Hyujeong. Thousands of righteous monks proved instrumental in expelling invaders and revitalized Joseon Buddhism despite centuries of suppression.