The 4th Battle of Kawanakajima between daimyos Uesugi Kenshin and Takeda Shingen during the Sengoku period in Japan - Kenshin used the "wheel" formation, where units that are exhausted are rotated to the back of the 'wheel' and replaced with a fresh unit. He realised that the troops at the front often got tired while the ones at the back waited as lines clashed, so he used this to his advantage. Once the troops in fight were worn out, they would move to the side and down through the ranks as the second unit moved up. According to the Koyo Gunkan (the military records of the Takeda), the Takeda army was close to defeat, but didn't break because Shingen himself continued to rally his soldiers.

The Ambush of Okehazama saw Oda Nobunaga outnumbered more than 10 to 1 against the opposing army, with a small force of roughly a thousand or so men in his castle. He raised more banners than what he had whilst also leaving a small garrison within, giving the impression that the castle was well fortified. With the rest of his force, he retreated into the forest and waited until the opposing army came up. When they did, he took them in the rear and caused a mass rout, effectively winning the battle.

The Mongols led by Genghis Khan originally set out to consolidate their power over Western China by first attempting to conquer the Xia - the Mongols followed the Yellow River up to the capital, Yinchuan. The garrison of the capital was more than double that of the Mongol army, and, being one of the first few attempts at siege warfare, the Mongols actually failed to capture the city. Instead, Temujin diverted the flow of the Yellow River to flood the city and the plains, wiping out their crops and forcing the Xia to submit.

Sources:

Kawanakajima 1553-64 - Turnbull, S.

The Samurai: A military history - Turnbull, S.

Genghis Khan and the Making of the Modern World - Weatherford, J.