Tadatsugu was born in 1527 to Sakai Tadachika, a hereditary vassal of the
Matsudaira clan of Mikawa Province. At some point during Tadatsugu's life,
Oda Nobuhide, father of
Oda Nobunaga, invaded and besieged Ida castle in Mikawa. Tadatsugu and
Naitō Nobunari were reportedly sallied out, fighting Nobuhide's army to defend the castle. It is said that after Hirotada's death, in 1551 Tadatsugu served young Ieyasu and was a hostage in
Sunpu. In 1556, according to the records from
Tosho Gunkan, Tadatsugu defended Fukutani castle, which was besieged by 2,000 cavalry troops of the Oda clan led by
Shibata Katsuie. Tadatsugu repelled the invaders by leading a sallying force outside the castle to engage Katsuie's troops. During this battle, Watanabe Yoshitsuna, maternal grandfather of
Watanabe Moritsuna, fought under the command of Tadatsugu and manage to kill Katsuie's general Hayakawa Tōta with a bow. In 1558, Tadatsugu accompanied Ieyasu in the
Siege of Terabe. In 1560 at the
Siege of Marune, Tadatsugu served as a vanguard of the Tokugawa forces along with Ishikawa Ienari. After a tough battle, he defeated
Sakuma Morishige, a general from the Oda side who was defending the fort. It was said that Morishige was killed with arquebus shots from the Tokugawa forces. In 1563, during the
Mikawa Ikkō-ikki uprising, Tadatsugu followed Ieyasu while his brother, Sakai Tadanao, chose to support the Ikkō-ikki. This religious uprising has four epicenters where the
Ikkō-shū radicals had fortified their temples. Tadatsugu were tasked with pacifying one of the garrisoned temples, which was located in Ida village. In the same year, Tadatsugu married princess Usui (Usui-Hime), grand-daughter of
Matsudaira Hirotada and Ieyasu's sister. In 1564, Tadatsugu lead an attack towards
Yoshida Castle, forcing the lord of the castle, Shizumi Obara, to escape and the castle to surrender without a fight. In the same year, before the
Battle of Azukizaka, Tadatsugu wrote a letter to the Ikko-Ikki faction in Mikawa, chastising their rebellious conduct.
Service in the Oda-Tokugawa alliance Sometime around 1565, Tadatsugu urged his superior, Ieyasu, to abandon his allegiance with the
Imagawa clan. After the Tokugawa clan captured
Yoshida Castle in eastern Mikawa (present-day
Toyohashi), Ieyasu ordered Tadatsugu to control the castle. By 1567, Ieyasu had reorganized the structures of his army into two divisions, each with a separate commander. Tadatsugu was placed over the forces of 18 Tokugawa
Fudai and
Kamon daimyōs, while Ishikawa Kazumasa was given command over the forces of 13
daimyō. such as
Matsudaira Ietada (Fukōzu),
Matsudaira Tadamasa,
Matsudaira Ietada (Katahara), and others. In 1569, Tadatsugu participated in the
Siege of Kakegawa castle. In 1572, during the
Battle of Mikatagahara, Tadatsugu fought the opposing
Takeda clan forces on the far-right position of the Tokugawa forces' stork-shaped formation. At first, Tadatsugu repulsed the first wave of the Takeda clan's charge led by
Oyamada Nobushige. However, as the second wave led by
Baba Nobuharu stepped in, units under Tadatsugu were overwhelmed. Tadatsugu struggled as his troops were badly beaten. As Ieyasu and his allies retreated to
Hamamatsu Castle, Tadatsugu participated in the ruse which mitigated the effects of Takeda victory in the field, and the Takeda forces withdrew. In June 1574, when the Takeda clan began
sieging Takatenjin,
Oda Nobunaga personally lead reinforcements. He encamped in Yoshida castle and was greeted by Tadatsugu. However, as he heard that Takatenjin had surrendered, Nobunaga aborted his trip to Takatenjin and returned to Yoshida castle to plan. In 1575, when
Takeda Katsuyori laid
siege to Yoshida castle, Tadatsugu defended with a garrison of 6,000 soldiers. The battles were exclusively limited to spear skirmishes outside the wall, which frustrated Katsuyori, causing him to abandon the siege. . Later in the same year, during the war council discussion before the
Battle of Nagashino, Tadatsugu suggested a night raid, which was quickly rejected by Nobunaga. However, Nobunaga talked with Tadatsugu in private after the council and gave him permission to execute the plan in secret, because Nobunaga was afraid that, if he publicly agreed with Tadatsugu's plan during the council discussion, it could potentially be leaked to enemy intelligence. Tadatsugu was tasked with leading a night raid against the Takeda forces located in Tobinosuyama with
Kanamori Nagachika. They led a
flying column of 2,000 Tokugawa archers and
arquebus gunners, which was further supplemented with the Oda clan's regiment of cavalry and 500 arquebus gunners. Tadatsugu led these forces to take the road from Koshu to Horai-ji Temple in Sanshu, then crossed a river, until they reached the camp of the Takeda forces near the besieged
Nagashino castle. Tadatsugu successfully ambushed the Takeda forces, which caused the death of two Takeda generals,
Takeda Nobuzane and
Saegusa Moritomo. After the enemy troops in Nagashino castle were routed, Tadatsugu also burned Kadoya village, nearby the location. and a
Maki no Tachi(sword's mounting). In 1578, Tadatsugu's son,
Sakai Ietsugu (1564–1619), took over his father's role as castellan of Yoshida Castle. In 1579, Tadatsugu was involved with a tragedy that befell the Ieyasu family, which ended with Ieyasu's wife,
Lady Tsukiyama, being executed, and their son,
Matsudaira Nobuyasu, being forced to commit
seppuku. Tadatsugu played a role in confirming Oda Nobunaga's suspicion of the alleged betrayal against the Oda clan being planned by Lady Tsukiyama, as Nobunaga concluded that, since a high-ranking fudai daimyō such as Tadatsugu had confirmed the accusation by testifying against Lady Tsukiyama, then the accusation must be true. Tadatsugu may have actually conspired with
Odai no Kata to get rid of Lady Tsukiyama.
Arthur Lindsay Sadler theorized that this was a deliberate act of spite from Tadatsugu due to his dislike of Nobuyasu.
After Nobunaga's death In 1582, after the
Honnō-ji Incident, Tadatsugu accompanied Ieyasu in
crossing Iga province and returning to
Mikawa to escape the enemies of Nobunaga in
Sakai. However, their journey was very dangerous due to the existence of
"ochimusha-gari" groups across the route. As they reached Kada, an area between
Kameyama town and Iga, the attacks from the ochimusha-gari ended as they reached the territory of
Kōka ikki samurai who were friendly to the Tokugawa clan. The Kōka ikki samurai then escorting them until they reached
Iga Province, where they were further protected by samurai clans from the
Iga ikki, which accompany the Ieyasu group until they safely reach Mikawa. In June-October 29 of the same year, the occurred among the Tokugawa clan,
Hōjō clan, and
Uesugi clan over control of the area of
Kai Province (currently
Gunma Prefecture),
Shinano Province (currently
Nagano Prefecture), and the Ueno region, which had been vacant since the destruction of
Takeda clan and the death of Oda Nobunaga. After Ieyasu returned to Mikawa, he led an army of 8,000 soldiers into Kai, Shinano, and Ueno, in order to annex it. However, an army of 55,000 men under the
Hōjō clan crossed the Usui Pass to invade Shinano. Ieyasu dispatched Tadatsugu and Ogasawara Nobumine with a detachment to pacify Shinano, while Ieyasu took the main army to pacify Kai. However, Tadatsugu and Nobumine met with unexpected resistance from Suwa Yoritada, a former Takeda vassal who was now allied with the Hōjō clan. They were defeated by Moritada, and Tadatsugu's army was almost encircled. Tadatsugu then led a desperate breakthrough and broke the encirclement. He retreated into Wakamiko in Kai province, where he rejoin Ieyasu's main forces. In Wakamiko, the confrontation lasted for 80 days without a clear result. During this period, Ieyasu acquired more than 800 former vassals of the Takeda clan from Kai. Later, in December, Tadatsugu led the army once again to subdue Suwa Yoritada at
Suwa in Shinano, where Tadatsugu manage to subdue Yoritada and secure his surrender to the Tokugawa clan.
Battle of Komaki-Nagakute In 1584, during the
Komaki-Nagakute campaign, Tadatsugu successfully turned back a move by
Toyotomi Hideyoshi's forces against
Kiyosu Castle, which was led by Hideyoshi's commander
Mori Nagayoshi. Tadatsugu scouted Nagayoshi's forces during their march, and as Nagayoshi rested and camped his soldiers in the Hachimanbayashi area of Haguro. Tadatsugu joined
Okudaira Nobumasa and
Matsudaira Ietada (Fukōzu) in Komaki to launch an attack at dawn. As they pushed Nagayoshi's forces, Tadatsugu tried to encircle them from the flank, killing 300 of Nagayoshi's soldiers. However, they ultimately failed to entrap Nagayoshi as he manage to breaking through the encirclement and retreat. Following this, Tadatsugu returned to Komaki where he, Honda Tadakatsu, and Ishikawa Kazumasa stationed their troops. After the battle of Nagakute in April, the front line in northern Owari reached a stalemate. At this time, Kanie Castle was located about three miles between Ieyasu's Kiyosu Castle and Nobuo's Nagashima Castle, and was connected to the Mie moat and three castles: Ono Castle, Shimojima Castle, and Maeda Castle. Kanie castle faced the sea and was one of the leading ports in Owari, along with Atsuta and Tsushima. On June 18, Ieyasu and Nobuo led 20,000 soldiers and besieged
Kanie, Maeda, and Shimojima. Kanie castle was defended by
Maeda Nagatane and
Takigawa Kazumasu. Tadatsugu, Okanabe Mori, and Yamaguchi Shigemasa spearheaded the attack of Shimojima castle, while Sakakibara Yasumasa, Osuga Yasutaka were deployed to capture any fleeing defenders. During this siege, Ieyasu's
Hatamoto retainers, including Mizuno Katsunari, blockaded the port of the castle, and hijacked two ships belongs to
Kuki Yoshitaka, to prevent any outside help for Kanie castle. After the fall of Shimojima castle, on June 22, Oda Nobuo and Tokugawa Ieyasu launched an all-out attack on Kanie Castle. The soldiers led by Tadatsugu, who had been deployed at the main entrance, were exhausted after days of fierce fighting, and in the evening, the soldiers of Sakakibara Yasumasa and Matsudaira Ietada entered Kaimonjiguchi. On June 23, Ieyasu entered the castle with Sakakibara Yasumasa, and the castles were subdued. In the following month, the three of them were joined by Tadatsugu Sakai to accompany Ieyasu in his personal trip to Kyoto, where the four of them "became famous".
Post retirement and Death In 1590, during the
Odawara Campaign, Tadatsugu was ordered to accompany
Tokugawa Hidetada, Ieyasu's son and heir, to
Kyoto, where he served as a hostage for Ieyasu's loyalty to the Toyotomi clan during that campaign. After the battle, Hideyoshi ordered the Tokugawa clan to relocate from their ancestral holdings to the
Kantō region. Tadatsugu went into retirement, but his son Ietsugu received a 30,000
koku fudai fief at Usui, in
Shimōsa Province, and Tadasugu accompanied him there. Tadatsugu died in
Kyoto in the winter of 1596. After Tadatsugu's death, the Sakai clan continued to prosper. == Personal info ==