By the end of the month, both should be before Tippoo's capital.

Siege will probably occupy a month.
"Even if Berar decides against us, its army cannot arrive in time to aid Tippoo.

Therefore, if you can extend the negotiations for a month after you receive this, your mission will have been fulfilled." This messenger had, of course, been sent off before the arrival of the troopers in Calcutta and, if Lord Mornington's calculations were correct, Seringapatam would be invested before they could return.

Three days later, indeed, a report reached Nagpore that Tippoo had fallen upon the advance guard of the Bombay army, and had been repulsed; and on the 27th he had attacked General Harris, and had again been defeated; and that on the 28th the main army had forded the Cauvery, and had marched to Sosilly.
This news caused great excitement in the town, although Seringapatam was generally supposed to be impregnable and, as the English had failed to take it during the last war, it was believed that, after another futile siege, they would be forced to fall back again from want of food, as they did upon the previous occasion.
The rajah, like the majority, believed that Seringapatam could defy any assault; and that, surrounded as the British army would be by the Mysore cavalry, they would very speedily be forced to retire; and that, although Tippoo might have yielded to the wishes of his general, and attempted to check the advance, it could have been with only a portion of his army.
Including the contingent furnished by the Nizam, the Bombay army amounted to forty-three thousand men.

Tippoo was credited with having at least twice that force, and his uniform successes against his neighbours had created a belief that he was invincible.