There are plenty of buddhists that do believe in demons and pagan gods; buddhism as just a philosophy is relatively rare. And in modern history buddhist fought the tamil hindus for 25 years, a war with thousands of deaths. But I guess you missed that somehow.
Buddhists can't, by definition, believe in demons and gods. If they do, they aren't Buddhists. "Issara-nimmana-vada", which in Pali means "supreme being, creator of creation", is an idea explicitly rejected by Buddha in the sutras.
As for war, in the Dhammapada, the earliest collection of the sayings of Buddha, chapter ten reads:
All living things tremble at violence; all living things fear death. Putting one in the place of another, one should not kill nor cause another to kill. All beings tremble at violence; life is dear to all beings. Putting one in the place of another, one should not kill nor cause another to kill. One who, while himself seeking happiness, oppresses with violence other beings, who also desire happiness, will not attain happiness by such. One who, while himself seeking happiness, does
not oppress with violence other beings, who also desire happiness, will attain happiness by such. Speak not harshly to anyone, for those thus spoken to might retort. Indeed, angry speech hurts, and retaliation may overtake you. If, like a broken gong, you silence yourself, you have approached wakefulness, for vindictiveness is no longer in you. Just as a cowherd drives the cattle to pasture with a staff, so do old age and death drive the life force of beings hence and fro. When the fool commits evil deeds, he does not properly realize their evil nature. The witless man is tormented by his own deeds, like one burnt by fire. He who inflicts violence on those who are unarmed, and offends those who are inoffensive, will soon come upon one of these ten states: Sharp pain, or disaster, bodily injury, serious illness, or derangement of mind, trouble from the government, or grave charges, loss of relatives, or loss of wealth, or houses destroyed by ravaging fire; that man resides continually in the state of suffering. Neither going about naked, nor with matted locks, nor in filth, nor fasting, nor lying on the ground, nor smearing oneself with ashes and dust, nor sitting on the heels in penance can purify a person who has not overcome doubt. Yet, even if a man be well attired, so long as he is posed, calm, controlled and established in the noble path, having set aside violence towards all beings — he, truly, is a holy man, a renunciate, a monk. Only rarely is there a man in this world who, restrained by modesty, avoids reproach, as a thoroughbred horse avoids the whip. Like a thoroughbred horse touched by the whip, be strenuous, be filled with spiritual yearning. By determination and moral purity, by effort and by meditation, by investigation of the truth, by being rich in knowledge and virtue, and by being mindful, dispel this unlimited suffering. Irrigators regulate the waters, fletchers straighten arrow shafts, carpenters shape wood, and the good control themselves.
So, as you can see, war is very much not part of Buddhist philosophy, nor is the idea of salvation "from above". As Buddha said "be lights unto yourselves, seeking no refuge from outside oneself; let striving diligently be your refuge, the Dhamma your island. Seek no other".
This kind of thing is why traditional Buddhist monks (like the monks in Sri Lanka or the mountains of Norther India, for instance) are never on the news for being violent. In fact, as a child I remember reading stories of Nazis murdering entire monasteries full of monks who didn't fight back; stories of monks who, rather than resort to violence, immolated themselves or practiced dry-death (eating seeds and nuts until the body literally self-mummifies).
Unlike the bible, Quran, or some of the Hindu scripts, Buddhism's text (the Dhammapada) is the only one that contains no instructions to violence
whatsoever.
Have you read the bible, and found who the cause for all those gods that men worship are? 
