Assalam Alaikum:
Very short and sweet answer. This reads very sensible. May Allah bless you.
Regards.
there were other means too. as pointed out by another poster. Indonesia for eg. wasnt conquered by sword
however, muslims did fight a lot in the cause of Islam. They defeated the Byzantines towards the west and the north and the Persians towards the east. At that time muslims were peoper muslims and they had commanders like Ali ra, Abu ubaidah ra, Khalid bin Walid ra and others. now we have pussycats like Mush.
here is a brief overview of how Islam spread by sword, blood and sweat.
to the west (of arabia)
Makkah, yemen, egypt and the holy lands all came to the muslims via the sword.
in the north
there was Constantinople and later Spain (Andalusia) and basically Europe was at the mercy of mamluks of Ottoman before they began fighting amongst themselves for power. Actually there is a famous hadith where the Prophet Muhammad (saw) praised the commander and army that conquers Constantinople. Therefore, every muslim caliph dearly wanted to be the one to capture turkey.
in the east
muslims conquered persia (present iran & Afghanistan) and later India (sindh) and much later ghauris and gahzanvis from Afghanistan attacked India. Then later came the mughals.
At that time Muslims armies used to regularly defeat roman and Persian armies which were much bigger in size and were far better equipped. Contrary to popular belief, most of the battles were offensive campaigns and the idea was to spread the message of islam far and wide. Alhamdullilah the early muslims kept their duty to Allah (swt) and today my country and i are muslim even though most of us have never been to Arabia!
Admittedly some of the later battles in the name of islam were not for islam. Instead the ruler had vested interest in it. However, it would a huge injustice to deprive the great mujaheddin and martyrs of their noble efforts by saying that islam wasnt spread by sword.
Details can be found any good history books.
proof of fighting to spread islam can be found in numerous hadiths and verses of the quraan. every muhaddith had dedicated a section for chapter for jihad, rules of fighting etc.
here are a couple of useful links
long
http://www.islamqa.com/en/ref/43087
short
http://www.islamqa.com/en/ref/5441