"the aim is to threaten and arm-twisted big banks into exchanging their bonds"

You're basically saying that Greece renegotiated some of it's debt obligations. Which is a default.

"Sovereign defaults Sovereign borrowers such as nation-states generally are not subject to bankruptcy courts in their own jurisdiction, and thus may be able to default without legal consequences. One example is with North Korea, which in 1987 defaulted on some of its loans. In such cases, the defaulting country and the creditor are more likely to renegotiate the interest rate, length of the loan, or the principal payments."

http://en.wikipedia.org/wiki/Default_(finance)#Sovereign_def...