Did Mohammad spare women and children in battle?

Muslims are very proud of the fact that, although Mohammad was a military leader and took part in many battles, he was always concerned never to harm women or children. There is, however, a worrying hadith for Muslims which suggests that Mohammad was not always so careful.
Bukhaari:V4B52N256 "The Prophet passed by and was asked whether it was permissible to attack infidels at night with the probability of exposing their women and children to danger. The Prophet replied, ‘Their women and children are from them.'"
Having been quoted the above hadith, "Kevin" asked me to check the authenticity and then find out what Muslim scholars had to say about it. He then suggested that possibly the women and children might have been enlisted to fight and were therefore legitimate targets. This was my reply:

I have checked the authenticity. [1]

I have also checked to see what the scholars[2] make of this hadith. “The only exception to this (the rule that women and children cannot be targeted) is where such people participate directly in the fighting or are so intermixed with the fighters that it is impossible to separate them from those who are fighting.” The trouble with this, of course, is that they’re only "intermixed" because the Muslims are attacking at night! And I would give more credence to your suggestion that the women and children might have been enlisted to fight against the Muslims and therefore could have been legitimate targets were it not for the questioner asking if were permissible to “expose them to danger” as a consequence/by-product of attacking at night. The simplest, clearest, most obvious explanation of this hadith, surely, is that Mohammad, as a ruthless warlord, was unconcerned with minimising casualties. 

[1] Here’s the page showing the hadith on an Islamic site: http://www.searchtruth.com/searchHadith.php?keyword=their+women+and+children+are+from+them&translator=1&search=1&book=&start=0&records_display=10&search_word=all

[1] http://www.answering-christianity.com/karim/no_killing_of_civilians.htm

So the evidence from this apparently utterly reliable hadith (I'm going on what Muslims have to say about the hadith here) is that Mohammad did not always spare innocents in warfare.