There are exemptions to certain groups of people for fasting in Islam. These exemptions are for women who are menstruating, pregnant, the elderly who are sick or are not able to fast, those who are traveling, pre-pubescent children, mentally challenged, and those who are engaged in battle.

Some of those people who fall in the categories mentioned above (including soldiers) would either have to make up their missed fasts throughout the rest of the year or give a certain amount of money away in charity. These are the Islamic principles as outlined in Orthodox Sunni and Shi'ite Islam.

As far as Arab soldiers during the October War, as far as I know, these soldiers from exempt from fasting which didn't hinder their fighting ability.

No, Islam provides for many exceptions to fasting(Usually to be made up through some other form of penance). The Arab soldiers broke their fast the day of Operation Badr.