First off, here's a good consolidation of what is out there:
http://www.cooperativeresearch.org/wot/iraq/forged_niger_documents.html#1%20%20%20%20%20%20%20How%20the%20documents%20were%20obtained.The documents were obtained in late 2001 from the Italians. They suggested that Saddam tried to acquire 500 tons of uranium-oxide.
I assume everyone knows how ridiculous and simple the forgeries were. One letter was on the wrong letterhead, references were made to Niger's obsolete 1965 constitution, and signatures of officials, who were in some cases no longer in power, had been poorly forged. The main import of the forged documents is even more ridiculous. All of the output of "yellow-cake" in Niger comes from two French-owned mines in Niger. All of the output is pre-sold to power companies in Spain, France and Japan. 500 tons is a ridiculously large amount that could not shipped out on the sly without anyone noticing. An IAEA official is quoted as saying the forgeries were so bad that his "jaw dropped". Another said inaccuracies were found "after a few hours of going at it with a critical eye".
The IAEA had requested the Documents since September 2002, around the time Colin Powell asserted the evidence in a closed door hearing at the UN. They did not receive them until February 2003.
THe US and the British had this information for many months. It consisted of childishly forged documents. They had to know the documents were false.
So how does this fit in with any discernible political strategy? The documents are turned over to the IAEA just in time for them to be declared fraudulent before the war, yet there is no noise made in the media about their presence in the SOTU address. So why use fraudulent documents in a nationally televised speech and turn them over to the IAEA to be discredited? This shows that Bush had an expectation the false nature of the documents would be ignored in the media. Why did Bush expect to get away with this, and how did he get away with it for so long? It seems he was set up to fight this war and then fall.