Bruce led Hull to two promotions and an FA Cup final appearance in 2014 to secure his place in club folklore.
But he reached the end of his tether after being prevented from strengthening his playing staff due to the club’s on-going takeover saga.
Club officials denied reports that a transfer cap had been imposed and that Bruce had been told no more funds would be available for new players.
But earlier this week, the Tigers confirmed talks to sell the club had been put on hold for the remainder of the transfer window.
The club’s failure to land Nick Powell, as their former Manchester United loan striker opted to join Championship side Wigan, proved to be the tipping point for Bruce.