First lets write the FULL verse
"So when you meet those who disbelieve [in battle], strike [their] necks until, when you have inflicted slaughter upon them, then secure their bonds, and either [confer] favor afterwards or ransom [them] until the war lays down its burdens. That [is the command]. And if Allah had willed, He could have taken vengeance upon them [Himself], but [He ordered armed struggle] to test some of you by means of others. And those who are killed in the cause of Allah - never will He waste their deeds." (47:4)
The command concerns engaging in war on the battlefield, since the arabic word (laqaytum) derives from l-q-y and the word liqa at times denotes "meeting, encounter" and at this instant it indicates "confronting on the battlefield." so the honourable verse is speaking about the confrontation between two armies in a battlefield NOT a terrorist group kidnapping unarmed civilians
The expression: "then bind a bond firmly [lest they flee]" is a reference to making doubly sure that the captives are bound firmly lest they liberate themselves and strike fatal blows.
The verse continues that Prisoners of war may not be slain following the end of the war (REMEMBER THAT..you are not allowed to kill a prisoner of war who was just fighting you and was ready to kill you so how about an unarmed civilian) but the leader of Muslims exercises his discretion to either ransom or exchange them for others or set them free non gratia. It is actually a kind of compensation to be borne by the enemy.
REMEMBER that hiding the rest of the verse is a proof of evil intentions towards Islam...They are NOT fighting Christians or USA or anything the fight is against Islam and DO NOT forget that they the Muslim Jordanian Pilot Moaath who they burnt alive and claimed too that it is for Islam.
Islam the religion of peace
To prove the evil intentions of those who are trying desperately to pin their crimes on Islam they FORGOT to mention that Muslims were ordered never to transgress and to be merciful and befriend everybody who does not attack them let me mention some examples to you:
From the holy Quran
1- "Allah does not forbid you to deal kindly and justly with anyone who has not fought against you for your faith or driven you out of your homes. Allah loves the just." (60:8)
2- "Fight in the cause of God those who fight you, but do not transgress limits; for God loveth not transgressors" (2:190) In addition, when the enemy inclines toward peace, Muslims are commanded to cease hostilities: "But if the enemy incline towards peace, do thou (also) incline towards peace" (8:61)
From the sayings of the prophet
When Prophet Muhammad sent his companions into battle he said "Go out in the name of God and do not kill any old man, infant, child or woman. Spread goodness and do well, for God loves those who do well."(Abu Dawood)
"Do not kill the monks in monasteries" or "Do not kill the people who are sitting in places of worship." ( Imam Ahmad) .
And the examples are so much more the above examples are just a sample to prove my point.