Quote from Samurai-archives.com:

NAGASHINO
28 June 1575 / Mikawa / Siege and Battle

Takeda Katsuyori (12,000)
VS
Oda Nobunaga (30,000)/Tokugawa Ieyasu (8,000)

In the summer of 1575, Takeda Katsuyori led his army into the Tokugawa domain and laid siege to Nagashino Castle, a locally important strongpoint that had changed hands a number of times in the past few years. The castle's defenders managed to resist the initial Takeda attacks and, thanks to the heroic efforts of a certain Torii Sune'emon, managed to alert Tokugawa Ieyasu of their plight, and the latter convinced Oda Nobunaga to commit to an all-out battle with the Takeda. When faced with the appearance of a numerically superior enemy force, Katsuyori, over the objections of his veteran commanders, opted to attack. Thanks to superior firepower (as many as 3,000 arquebuses were used in the battle) and good positon, Oda Nobunaga and Tokugawa Ieyasu crushed the Takeda attack and relieved Nagashino Castle. Most of the famous Takeda generals present were killed in the battle and the offensive power of the Takeda was severly crippled (having lost around 10,000 men). Oda was now free to fully turn his attentions elsewhere, leaving Ieyasu to contain the battered Takeda. /Quote

I think this battle that lead in the downfall of the Takeda Clan was complete foolishness from Takeda Katsuyori.He could never fit in his great fathers Takeda Shingens shoes and in the end that resulted into destruction of the Takeda clan.