Serve your nation that sounds as if a neta is speaking. Well all good wishes. Let us talk of the consequences of resignation.
All the companies are aware of 'attrition' and are well prepared. The salary that was offered to and accepted by you sounds as if your company was not in the mould of best IT companies. Thus, if the matter is not resolved by talking to your HR, the company can sue you. In their meanness, they can become nasty. Think of the consequences of running from your new posting in Central Government and old company to attend the case in a civil court.
You were not provided training and you are a self made man and have earned money for the company are statements that hold no water. They have violated the terms of the bond that is what you say.
My humble advice (remember the cheapest thing in this world is advice which no body likes) is to talk to HR before joining the new job. If he is adamant, things would not be as rosy as advised.