I couldn't resist sharing this story from an AMA special interest group. Great play on behalf on one brand to limit the impact of another encroaching brand

Q: I was hoping someone could point me in the direction of an information resource (preferably case studies) that speak directly to strategies/best practices under taken by a dominant brand in a product
category to defend against the impending launch of a new brand from a major competitor.

The established Brand product was ArmorAll(R) protectorant for leather, plastics and rubber, sold in the auto aftercare market. The new competitive product, STP "Son-of-a-gun" was introduced into a test market, and the ArmorAll brand reacted with a "Buy-one-get-one" sale. When consumers faced the two products, side by side on the shelf, the ArmorAll sold, and the STP was left. The test market was considered such a failure by STP, that company support for the product was reduced, and it was years before another attempt was made to gain significant market share.

ArmorAll did give away product during the promotion, but was able to control the market with an offer consumers could not refuse. And since one bottle of ArmorAll could typically last for years, the two bottle promotion effectively removed that customer from the STP prospects for quite some time.