Surah Muhammad, which is also known by the title "fighting", 
            testifies to the fact that Prophet Mohammed, 
            peace be upon him, was a Prophet of mercy as well as combat; 
            he is with the oppressed against the oppressor, and with the victim 
            against the wrongdoer. In order to appreciate the context of these 
            verses one has to think how oppressed people, in Bosnia, Palestine 
            or Iraq, feel towards the oppressors who have usurped their land, 
            slaughtered their men, raped their women and/or trampled on their 
            human rights.
          Muslims used to recite passages from this Surah during 
            combat as it has a special pounding rhythm that aroused fear in the 
            hearts of their enemy. 
          Necessity of Obedience for 
            Deeds to be Accepted
          For deeds to be beneficial and for them to yield good 
            results, they would depend entirely 
            on the person's obedience to Allah and His Messenger. 
            After one has turned away from obedience, no deed remains a good deed 
            and hence one does not deserve any reward for it.
           Imam Ibn Kathir indicates that disbelievers can never 
            harm Allah in the least, and rather they only harm themselves and 
            become losers on the Day of Resurrection. Allah will not reward them 
            even the weight of a mosquito (i.e., the smallest thing) for any good 
            that they did before their apostasy, but would instead totally invalidate 
            and destroy it. Their apostasy wipes 
            away their good deeds entirely, just as the good deeds would normally 
            wipe away the evil deeds. 
          Appealing for Peace ?
          One should bear in mind the context of this revelation. 
            These Ayahs were revealed when only a handful of Muslims in the town 
            of Medina were standing up for Islam, and they were up against not 
            only the Quraish but also the rest of pagan Arabia. This was the condition, 
            when they were asked "not to be faint-hearted and not to beg 
            for peace,", but to make preperation for decisive conflict. This 
            does not, however, mean that Muslims should never negotiate for peace. 
            In a situation like the one detailed 
            above, it is not right for Muslims to initiate peace negotiations, 
            since it would be testament to the Muslim's weakness. 
            This would further encourage the enemy. Hence, Muslims should first 
            establish their superiority in power and strength; and then negotiate 
            for peace. And all the while we need to remember that Allah is on 
            our side and He would reward us for our deeds, and would not let it 
            go to waste like in the case of the disbelievers.
          Sources:
            "Thematic Commentary 
            on the Qur'an" - Muhammad al Ghazali
            "Tafsir ibn Kathir" - Imam ibn Kathir
            "The Meaning of the Qur'an" - Syed Abul Ala Maududi.