If the Muslims are merciful, why are there wars in the name of Allah?

I don't know where Muslims get the idea that they are merciful. Their harsh judgements and penalties under Sharia law would be enough to make anyone realise that they are far from merciful. Even Mohammed (Peace be upon him) showed little mercy to those he violently subjugated unless they were women to whom he extended the 'offer' of ual slavery or forced marriage.