Tokugawa Ieyasu
Before the start of the Edo period a shogun named Tokugawa Ieyasu united Japan thus creating an era of peace.
It was unified politically.
sekigahara
emperor tojo
Japan was eventually unified under Tokuagwa Ieyasu after his defeat of the final vestiges of the Toyotomi family at the Battle of Osaka in 1614 & 1615. This was the culmination of what is referred to as the Sengoku Jidai, or, Warring States Period, in Japan.
Unified military forces of Japan are called Japan Self-Defense Forces. JSDF, occasionally referred to as JSF or SDF.
Japan was not a unified country in its early days. There were multiple kingdoms whose enemies were the other kingdoms.
A unified Italy was built around the nucleus of the kingdom of Sardinia. Italy was unified in the year 1861.
i think it's because Japan was not unified , so it's priority was solving internal problems, i'm not sure
2000BC
You might be referring to the end of the age of warring states, when Tokugawa Ieyasu 'unified' Japan. This was in the early 17th century.