"And when the son of Mary is quoted as an example, behold! The folk laugh out, and say: Are our gods better, or is he? They raise not the objection save for argument. Nay! but they are a contentious folk. He is nothing but a slave on whom we bestowed favor, and we made him a pattern for the Children of Israel. And had we willed it we would have set among you angels to be viceroys in the earth". Quran [043.057-060]
Not equal are those believers who sit (at home) and receive no hurt, and those who strive and fight in the cause of Allah with their goods and their persons. Allah hath granted a grade higher to those who strive and fight with their goods and persons than to those who sit (at home). Unto all (in Faith) Hath Allah promised good: But those who strive and fight Hath He distinguished above those who sit (at home) by a special reward,- Quran [004.095]
O ye who believe! if any from among you turn back from his Faith, soon will Allah produce a people whom He will love as they will love Him,- lowly with the believers, mighty against the rejecters, fighting in the way of Allah, and never afraid of the reproaches of such as find fault. That is the grace of Allah, which He will bestow on whom He pleaseth. And Allah encompasseth all, and He knoweth all things. Quran [005.054]
Or think ye that ye shall be abandoned, as though Allah did not know those among you who strive with might and main, and take none for friends and protectors except Allah, His Messenger, and the (community of) Believers? But Allah is well-acquainted with (all) that ye do. Quran [009.016]
O ye who believe! Take not my enemies and yours as friends (or protectors),- offering them (your) love, even though they have rejected the Truth that has come to you, and have (on the contrary) driven out the Prophet and yourselves (from your homes), (simply) because ye believe in Allah your Lord! Quran [060.001]
When ye travel through the earth, there is no blame on you if ye shorten your prayers, for fear the Unbelievers May attack you: For the Unbelievers are unto you open enemies. Quran [004.101]
Let not the unbelievers think that they can get the better (of the godly): they will never frustrate (them). Against them make ready your strength to the utmost of your power, including steeds of war, to strike terror into (the hearts of) the enemies, of Allah and your enemies, and others besides, whom ye may not know, but whom Allah doth know. Whatever ye shall spend in the cause of Allah, shall be repaid unto you, and ye shall not be treated unjustly. Quran [008.059-060]
Yes, there are wars in the old testament (please remember that Israel is Israel and not the church) and the concept of a 'holy war' is not biblical. It's just that some church leaders came up with it way later. I wouldn't count it as christian doctrine.
The God of Islam, Allah, is most definitely not the God of the Bible. Allah is presented in the Koran as an autocratic ruler who is aloof and arbitrary (Sura 5:40). Allah is unknowable whereas the God of the Bible is knowable (2 Timothy 1:12). Allah is unitarian (Sura 4:48) whereas the God of the Bible is trinitarian (2 Corinthians 13:14). Here is what the Koran says about the God of the Bible (Sura 4:171):
"Believe in Allah and say not 'Trinity.' Cease! It is better for you! Allah is only One God. Far is it removed from his transcendent majesty that he should have a son."
Allah is capricious (Sura 2:284), whereas the christian God is trustworthy. And Allah is never anywhere presented as a god of love ? which is the essence of the nature of the christian God (1 John 4:7-16).