Egyptian security under pressure
Pan a camera round the streets of central Cairo during the past few days and the visible security presence is uniformly khaki.
The Egyptian army arrived in force last week with their columns of US-designed M1Abrams tanks, made in Egypt under licence.
US-made F16 jets briefly buzzed the crowd at the weekend while an old Russian-made helicopter clattered overhead.
The arrival of Egypt's military has been welcomed by the protesters, especially since a military spokesman announced late on Monday that "it respected the people's rights to legitimate protest" and that "it has not and will not fire on protesters".
The black-clad riot police who laid into protesters with such ferocity last week vanished from sight, like hyenas backing off from a carcass when a larger predator turns up - their unpopular boss, Interior Minister Habib al-Adly, sacked by President Hosni Mubarak in his cabinet reshuffle.
But out of sight and behind the scenes, there are complex calculations taking place in Egypt's military and security apparatus.
For decades, the Egyptian government has employed a small army of security people to shore up the power of the "rais", the president, and his government.'Human rights abuse'
There is the uniformed presidential guard, the Haras al-Gumhuriya, distinguished by their bright blue berets as they stand guard at palaces and presidential functions.
But there is also a more sinister and feared secret police force, the Amn al-Dawla (state security), staffed by burly men in faux-leather jackets who chainsmoke local cigarettes and for whom human rights is often a distant concept.
International human rights groups say the abuse of Egyptian prisoners is routine.
A notorious and horrific video taken on a mobile phone in a police station of a man being tortured into submission with a broom handle was widely circulated on the internet a few years ago.
Although, like all countries in the region, Egypt denies any complicity in torture, there is no question that the fear of falling into the hands of brutal government interrogators has helped sustain this president and those around him in power.Hidden forces
This is why it has been so remarkable to see so many Egyptians suddenly lose their fear of arrest by coming out on the streets to call publicly for President Mubarak to go, encouraged by events in Tunisia and delivering the calculated Arab insult of beating his portrait with a shoe.
So while the protesters certainly seem to be making the running and the powerful military appears to be backing them, there are still hidden forces in Egypt that have a vested interest in maintaining the status quo and frustrating any move to a genuine democracy.
Even if President Mubarak is forced to step down, as many expect, those who work in the state security sector will be hoping that the system he has created, based on emergency laws brought in 30 years ago, survives in some form.
Their biggest fear will be a backlash, the sort of public retribution meted out by the masses that was seen in Romania on the hated Securitate in 1989.
In an echo of East Germany that year, there are already reports of secret interior ministry files being burned in haste.