Although Chaim answered the question about the Jewish view of war I am going to provide the following information which specifies what the Torah says about war:
http://www.chabad.org/library/article_cdo/aid/1188343/jewish/Melachim-uMilchamot.htmHILCHOT MELACHIM U'MILCHAMOTEIHEMTHE LAWS OF KINGS AND THEIR WARSThis text includes 23 mitzvot; ten positive commandments and thirteen negative commandments. They are:
1) The obligation to appoint a king in Israel;
2) The prohibition against appointing a convert as king;
3) The prohibition against the king marrying many wives;
4) The prohibition against the king accumulating many horses;
5) The prohibition against the king amassing too much silver and gold;
6) The obligation to destroy the seven nations living in the Land of Canaan;
7) The prohibition against allowing any one of them to remain alive;
8) The obligation to destroy the descendents of Amalek;
9) The obligation to remember what Amalek did;
10) The prohibition against forgetting Amalek's evil deeds, including his ambush against the Israelites during their journey from Egypt to Israel;
l l) The prohibition against dwelling in Egypt;
12) The obligation to offer peace to the inhabitants of a city when besieging it; to carry out the laws governing the siege as prescribed in the Torah, in particular, the laws applying if the enemy agrees to surrender and those applying if it refuses;
13) The prohibition against offering peace to Ammon and Moab, in contrast to other nations, when besieging them;
14) The prohibition against destroying fruit-bearing trees during a siege;
15) The obligation to set up a latrine outside an army camp;
16) The obligation to carry a spike to dig with;
17) The obligation to anoint a priest to speak to the troops in the event of war;
18) The obligation to allow those who have consecrated wives, built houses, or planted vineyards to rejoice in their new status for a complete year, while releasing them from military conscription;
19) The prohibition against asking those mentioned in the previous category to perform any duties, including handling the needs of one's city or providing supplies to the troops during that year;
20) The obligation not to become frightened, nor to flee in the midst of battle;
21) The prohibitions and obligations regarding a yefat toar, a Gentile woman with whom the Torah allows relations in wartime;
22) The prohibition against selling a yefat toar;
23) The prohibition against subjugating her to perform menial duties after having relations with her.
These mitzvot are explained in the coming chapters.