3. Why did the policy of the Abe government to purchase government securities help to drive down the value of the yen? What was the mechanism at work here?

During the first half of the 2000s, the Japanese yen was relatively weak against the U.S. dollar. This was a boon for Japan’s export-led economy.
On January 1, 2008, it took 122 yen to buy one U.S. dollar. For the next four years, the yen strengthened relentlessly against the dollar, hitting an all-time record high of ¥75.31 to the dollar on October 31, 2011. The reasons for the rise of the yen were complex and had little to do with the strength of the Japanese economy because there has been very little of that in evidence.