There where four bombers that where designed for the 1944 jet bomber specification
north American flew the B-45 on 17 Mar 1947. As was mentioned first it was the first all jet bomber in active service.
Convair built one B-46, it was rejected from service after one was built because of concerns regarding it's narrow cabin being able to hold all the mission equipment. It first flew on the 2nd of April of 47.
The Boeing B-47 was the most successful of the lot but didn't fly until 2nd of December of 1947 and didn't enter squadron service until the B models came around Circa 1950.
Martin flew the B-48 bomber prototype on 22 July of 1947, two where built and it was rejected for service
And last but not least consider the Northrop B-49. Aka the jet powered Flying Wing.
The first conversion of the piston powered flying wing flew on 21 October 1947. Two where built, one of which crashed near Muroc Dry lake in California. The crew was killed, and the air force base that is located there is named after the pilot, Capt Edwards.
So why did I put all of this up, to point out that the B-47 wasn't the first all jet bomber in Squadron service, nor was it the first or second jet bomber design to fly. It was the fifth, and I haven't even gone and checked if there where some medium bomber designs or strike aircraft that where on the books or flying. It arguably wasn't even the most advanced or daring of the designs.
But there is no doubt that it was the most successful design to come out of the 1944 jet bomber specification.
The B-45 I belive was used in Korea as a recon platform. And years later it was confirmed that recon B-47's did see combat action and where shot down by the Soviets during the cold war. So I guess that counts as combat too.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.