DUBLIN—With doubts swirling about the solvency of the Irish state in early September, Finance Minister Brian Lenihan summoned a dozen senior government and bank officials to a conference room nicknamed the "torture chamber," a nod to its history as a venue for painful meetings.

For two years, Ireland had poured money on a raging banking crisis, to no avail. Each estimate of the rising price of rescuing Ireland's banks turned out too low. Mr. Lenihan needed to halt the drip-drip of bad news that was leading his country to ruin....