Protesters demonstrating for and against Hosni Mubarak clash in Cairo’s Tahrir Square on Wednesday
There is no single emotion that defines a revolution. Across Cairo, 30 years of autocracy are pouring out in streams of tears and screams of joy.
But the hope, fear and uncertainty coursing through the Egyptian uprising is shaking Israel.
Peace with Egypt under President Hosni Mubarak has been, according to one defence official, "Israel's second biggest strategic asset after the United States".
Now, some Israeli strategists are worried. "If there are open elections there, the Muslim Brotherhood will certainly take power. They are the only well-organised party there and if they get in, we will have another Iran, this time on our immediate border," said one defence official.
This view was echoed earlier this week in a secret memo that the Israeli Foreign Ministry sent to its ambassadors in major capitals.
The missive instructed diplomats to urge world leaders to support President Mubarak and not leave him in the lurch.
While the Israeli government swiftly reassesses its security, diplomatic and economic ties to Egypt, the IDF has been maintaining close links with the Egyptian military over the past week.
"These links are absolutely crucial to us and if they are harmed, it would have a critical affect on our national strategy," said one senior IDF officer this week.
The Camp David Accords, signed with Egypt in 1978, have allowed the IDF to scale down its forces significantly, a great saving to the Israeli economy and releasing the army from the fear of having to fight a war on multiple fronts.
In recent years, with the Hamas takeover in the Gaza Strip, the security alliance between the two countries has taken on added significance.
Egypt views Hamas with great suspicion due to its ideological ties to the Muslim Brotherhood, the main opposition group in Egypt and which is dedicated to Mr Mubarak's downfall.
The country has co-operated with Israel over the blockade of Gaza, with a view to weakening Hamas control. Egypt has also cracked down on terror activities in Sinai, directed at targets both in both Israel and Egypt.
Egypt maintains uneasy contacts a prisoner swap to release captured soldier Gilad Shalit. Another less-mentioned alliance between the two countries is against Egypt's biggest rival for Middle East hegemony, Iran.
Not all Israeli diplomats are concerned about the situation in Egypt, however. "We have a good and long relationship with Mubarak," said one senior Israeli representative, "but we have to realise that finally, his rule is coming to an end and it doesn't seem that he will be able to control the choice of his successor. We have to get ready for these changes and it may not be for the worse. A democratic government may well surprise us and even the Muslim Brotherhood could prove to be more open once it has to shoulder part of the responsibility for Egypt's future."
Some IDF and intelligence experts also share this optimism. "The panic is unwarranted," said one officer, "we were going to have to prepare for a transition period in Egypt anyway, and so far, there is no sign that this is an Islamic revolution. We might even end up with a better situation."
Many in Israel took heart at the choice of Mubarak's new deputy president last Saturday, General Omar Suleiman, a key figure in the defence relationship between the two countries.