The Arab-Israeli War in 1973, besides the Jewish Holiday, also took place during the Islamic holy month of Ramadan, during which practicing Muslims observe mandatory daytime fasting. Did this affect the performance of the Arab (Egypt and Syrian) armies? I'd think hungry or dehydrated soldiers may not fight or think as well as when they're well fed. Why did the Arab leaders decide to attack during this period?
Reasons for Arabs starting the war during Ramadan:
Arab attacked Israel on October 6, 1973. That year, October was the month of Ramadan. But the main reason for attack on this day was Yom Kippur festival, which was on this day. Yom Kippur also known as Day of Atonement, is the holiest day of the year for the Jewish people.
Arabs were defeated in all previous wars with the Israel.
So, Arab (Egyptian and Syrian) military forces launched an attack knowing that the military of Israel would be participating in the religious celebrations associated with Yom Kippur. Therefore, their guard would temporarily be dropped.
The other reason may be Battle of Badr, which was fought by Muhammad himself in the month of Ramadan. This may have considered by Arabs as a good precedent. (I am just speculating this, as the plan to attack Israel was code-named Operation Badr).
Ramadan fasting and Performances:
I tried lot for getting some authentic sources and information on this part of Yom Kippur war or Ramadan War, but yielded no positive results.
So, I am just drawing some conclusions, or you may called it speculations, based on the circumstantial evidences :
As said by bhau, the main impetus for the day of the attack was to coincide with a religious festival of the Israeli side, for advantage.
In my reading on this war, the issue of Ramadan did not come up as a significant factor, nor did the Arab side show signs that would indicate severe supply or troop quality issues. The initial attacks, especially on the Egyptian side, were expertly performed and the first engagements were a rude surprise for the IDF. It took time and hard fighting for Israel to finally gain the upper hand, cross the canal and force an armistice in about 30 days. Syria also made gains in the Golan before being driven off.
The earlier 6 Day War was a stark contrast. Then Israel used a holiday as a cover for a preemptive attack on the Arab side. The initial defeat and confusion did separate many Arab troops from food and water in the desert and the suffering was intense. The Arab armies essentially fell apart in days. Not having water is a serious issue in the Sinai Desert.
The mixed results gave both sides some pause for thought. While Egypt showed themselves they could contend for a time, the quick end to the war did save them from an embarrassing surrender of an entire Army. Israel had suffered worrying losses and their enemies were performing better. Sadat parlayed his relatively good showing into a more secure rule at home which in the end gave him the status to be able to gain the Sinai back at the peace table.