The company is expected to challenge his demand for compensation for loss of office, to claim he was responsible for some of the lingering problems at its troubled Elvi chain, and to contest his valuation of the company at pounds 26.8m, calculating that a price of 170p per share would be fairer than the 140p on offer from his company, Ciro Holdings.
The compensation claim stems from Mr Shannon's abrupt departure last year, shortly after Country Casuals issued a profits warning. Both sides agree that the split followed his insistence that his pounds 106,000-a-year rolling contract be doubled in length to two years.
In its offer document, Ciro said that if its bid succeeds, Country Casuals will - in addition to giving him a fixed two-year contract worth pounds 152,000 annually - give him pounds 128,100 to settle the compensation claim. less than Mr Shannon's original outstanding demand for pounds 170,000.
But sources close to the company said the only formal outstanding claim it is aware of from Mr Shannon was one before an industrial tribunal, which would involve a maximum payout of just over pounds 12,000.
The acrimonious fight between former friends has already begun to focus on the Elvi chain, which sells clothes to larger women. Ciro said at the weekend it plans to convert or sell the Elvi shops within six months of taking over.
Management countered that the loss-making chain was making progress, said it remained committed to the venture, and complained about the "uncertainty" created by Ciro's announcement.
In the defence document, due out by Thursday, it is expected to escalate the bitter debate by claiming that much of Elvi's trouble is due to onerous leases signed while Mr Shannon was at the helm. Mr Shannon will probably counter that management has had a year to turn things around but has not.