The Holy verse says:
"Fighting has been enjoined upon you while it is hateful to you. But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah Knows, while you know not." (2:216)
When you read the verse lets first notice the following:
1- The verse is mentioning "Fighting" NOT "Attacking" or "Conquering" which means that:
2- This verse is not revealed for any specific war, it is actually revealed to prepare Muslims for what they will face in the future. They will be obliged to "fight" to preserve their faith.
3- Remember the word "hateful to you", which means Muslims hated war and did it only when they had to, so they are NOT blood thirsty vampires, they are people who are ready to sacrifice their lives to maintain their faith if someone attacked them. Also in the past, the fighter had to prepare his own horse and his own weapon which was considered a big financial sacrifice especially when you know that lots of the Muslim fighters then were poor.
4- This verse reflects God's profound understanding of human nature. He does not expect Muslims to be fearless and unaffected by the word "war". He understands that war is difficult as its price is very high because one can lose his life in it, so He tells Muslims that He knows war is difficult but He is teaching them not to judge by their shallow knowledge because God's knowledge is incomparable to ours.
5- This verse is very strongly related to the verse just before it that says:
"They ask you, [O Muhammad], what they should spend. Say, "Whatever you spend of good is [to be] for parents and relatives and orphans and the needy and the traveler. And whatever you do of good – indeed, Allah is Knowing of it." (2:215).
These two verses represent means of sacrifice for the sake of Islam. Verse 2:215 is the sacrifice by money (by showing who you can give charity to) while verse 2:216 shows the sacrifice by life (in war).
6- If you are a strong military force then when you think "war" you think "bounty", but when your army is weaker than those you will face you think you may die, that's when you need encouragement. That is what God did in this verse, encourage Muslims to defend themselves in war even if they think they are outnumbered.
This is very similar to the case in verses (2:249-250) the verses say:
"And when Saul went forth with the soldiers, he said, "Indeed, Allah will be testing you with a river. So whoever drinks from it is not of me, and whoever does not taste it is indeed of me, excepting one who takes [from it] in the hollow of his hand." But they drank from it, except a [very] few of them. Then when he had crossed it along with those who believed with him, they said, "There is no power for us today against Goliath and his soldiers." But those who were certain that they would meet Allah said, "How many a small company has overcome a large company by permission of Allah. And Allah is with the patient." "So they defeated them by permission of Allah, and David killed Goliath, and Allah gave him the kingship and prophethood and taught him from that which He willed. And if it were not for Allah checking [some] people by means of others, the earth would have been corrupted, but Allah is full of bounty to the worlds." (2:249-250)
In the two above verses God is giving Muslims a real life example to encourage them not to be afraid of war even when outnumbered. Notice the part "But those who were certain that they would meet Allah said, "How many a small company has overcome a large company by permission of Allah. And Allah is with the patient."
Do you truly believe that Muslims would wage offensive war against enemies who are more equipped and who outnumber them just for fun and greed. I think they were much more intelligent and realistic than that, they would fight ONLY when they have No other choice or when they were being attacked that's why fighting was then "hateful" to them.