Ferozeshah, fought on 21 and 22 December 1845, is the battle the British came closest to losing in India.
The Sikh position was entrenched with heavy artillery. The British attacked late in the day, took part of the camp, and spent the night in the open among the guns, out of ammunition, with units broken up and no clear command. Officers destroyed papers. The Governor General and the Commander in Chief were both on the field.
At dawn the attack was renewed and the position was taken. Then a fresh Sikh force under Tej Singh arrived, engaged briefly, and withdrew. Contemporary British accounts state plainly that if it had pressed the attack the British army would have been destroyed.
Tej Singh was in communication with the British before and during the war. Whether the withdrawal was betrayal, incompetence or caution is argued and the evidence points hard in one direction.
British casualties were around 2,400. It is remembered in the British Army as one of the hardest actions it fought in the nineteenth century, and in Punjab as the night the war was lost by the men commanding it rather than by the men fighting it.
It was fought on 21 and 22 December 1845 and it came closer to destroying a British army than anything else in the nineteenth century in India.
The British spent the night on the field between two Sikh positions, without water or supplies, and the reserve force under Tej Singh withdrew in the morning instead of attacking.
That withdrawal decided the war. Whether it was incompetence or arrangement is the question every account of the battle has to answer, and most of them answer it the same way.