An emphatic sentence puts the stress on an auxiliary verb instead of some element after the verb, a complement or modifier. In normal intonation, we might say something like "The President was traveling to EGYPT yesterday," thus stressing how the President spent the day. If someone doubted the veracity of our statement, however, we might make our statement more emphatic by placing the stress of our intonation on the auxiliary: "The President WAS traveling to Egypt yesterday." In the absence of an auxiliary, the verb "do" is used to create emphasis: "The President DID spend the day in Egypt." The "to do" form has no effect on the meaning of the sentence except that it adds emphasis. Click HERE for more information of the uses and forms of the "emphatic do." Emphatic sentences are seldom used in academic, formal prose.