Is this the same place where the book ends as well?
The main part of the book ends with tying up the stories of Yabu, Fujiko, etc., while Toranaga is still mobilising his troops for some future campaign. Then there is a one page epilogue where it said that Toranaga won at Sekigahara and 40k heads were taken. Here's the showdown you were looking for, in full.
"That year, at dawn on the twenty-first day of the tenth month, the Month
without Gods, the main armies clashed. It was in the mountains near
Sekigahara, astride the North Road, the weather foul—fog, then sleet. By
late afternoon Toranaga had won the battle and the slaughter began. Forty
thousand heads were taken."