The 'Underlying Business Transaction Details' means any transaction, contract or agreement made between the parties involved in the trade dealings. This is the Object of contract that specifies the goods/services covered by the Guarantee. 

The Bank cannot object to the underlying transaction, that is the guarantor pays upon the first written demand (recourse) of the beneficiary against presentation of confirmation as specified in the guarantee text and any required documents.

Although the Guarantee is independent from the underlying transaction between the parties, it exists as a support to the transaction.