We have no idea what went on behind the scenes before the announcement on Sunday that Mohammed Morsi, the candidate put forward by the Muslim Brotherhood, had won the presidency of Egypt over former Mubarak-era prime minister Ahmed Shafiq. But it is likely that there was at least tacit agreement between the army and the Brotherhood that any transformation of Egypt into a sharia state would not undermine the perogatives of the military.

Reuters:

Islamist Mohamed Morsy of the Muslim Brotherhood was elected president of Egypt with 51.7 percent of last weekend's run-off vote, defeating former general Ahmed Shafik, the state election committee said on Sunday.

"President Morsy will struggle to control the levers of state," Elijah Zarwan, senior policy fellow at the European Council on Foreign Relations, said in Cairo.

He succeeds Hosni Mubarak, who was overthrown 16 months ago after a popular uprising. The military council which has ruled the biggest Arab nation since then has this month curbed the powers of the presidency, meaning the head of state will have to work closely with the army on a planned democratic constitution.

Thousands of Brotherhood supporters burst into cheers on Cairo's Tahrir Square, waving national flags and chanting "Allahu Akbar!" or God is Great, greeting a dramatic victory.

Morsy, a 60-year-old, U.S.-educated engineer who spent time in jail under Mubarak, won the first round ballot in May with a little under a quarter of the vote. He has pledged to form an inclusive government to appeal to the many Egyptians, including a large Christian minority, who are anxious over religious rule.

The military council will retain control of the biggest army in the Middle East, whose closest ally is the United States. Morsy has said he will respect international treaties, notably that signed with Israel in 1979, on which much U.S. aid depends.

There is no constitution to define the president's powers - only a vague "constitutional decree" issued by the military before the vote last weekend. The military will now set up a constitutional assembly to write a new document. The assembly will probably have token representation of Islamists and liberal secularists, but be dominated by military-friendly members. Then a new parliament will be elected that will almost certainly be less Islamist than the previous one.

Will Morsi and the Brotherhood accept all of this? When you consider who has the guns and tanks, they may feel they have no choice. But I wonder what the military thought of this.