"Kenya Troops Off To War", screamed the headline in Kenya's Daily Nation newspaper.
Kenya has in the past trained Somali troops for deployment near the border to create a buffer zone in an effort to keep al-Shabab militants away, but the presence of Kenyan soldiers inside Somalia has always been played down or even flatly denied.
The very public announcement of this incursion into Somalia by the Kenyan army and air force is a significant change of policy, which seems at least partly aimed at sending a message to the Kenyan people and the rest of the world that the issue of security is being taken seriously.
"Our territorial integrity is threatened with serious security threats of terrorism. We cannot allow this to happen at all," Kenya's Internal Security Minister George Saitoti told the media.
"It means we are now going to pursue the enemy, who are the al-Shabab, to wherever they will be, even in their country."
The operation - unprecedented for Kenya's largely inexperienced military - appears to have been triggered by the recent kidnappings of four foreign nationals and one Kenyan.
Two of them were taken on the north Kenyan coast and the others in the Dadaab refugee camp near the border.
There is, however, no concrete proof that these kidnappings were carried out by the Islamist insurgent group.
In an area plagued by guns and Somali bandits, blaming al-Shabab could be jumping to a convenient conclusion.
Some analysts think the military operation is not about rescuing the hostages but is actually about securing the border
Going after a group linked to al-Qaeda and which is on the US terror list is an easier sell to the public than chasing bandits inside Somalia.
'Excuse they need'
The verbal response from al-Shabab was swift.
"Mujahideen fighters will force them to taste the pain of the bullets," an al-Shabab official said, after the Kenyan incursion was made public.
For ordinary Kenyans there is some concern that, should the military get embroiled deeper in Somalia's complicated war, it could make Kenya more of a target for groups like al-Shabab.
The fact that Uganda fell victim to deadly bombings last year for the role it has played with the African Union force in Somalia has not gone unnoticed.
"This Kenyan action may give the al-Shabab hardliners the excuse they needed to justify a strike against Kenya," said Rashid Abdi, a Somalia analyst with the International Crisis Group.
Clearly the Kenyan government could not sit back and do nothing after the kidnappings but Kenyans hope this is a very short-term operation lasting maybe just a few days.
Somalia's government troops, some trained by Kenya, have also been battling al-Shabab near the Kenyan Somali border and they do not want to be portrayed as impotent forces in need of foreign help.
With Ugandan and Burundian soldiers propping up the Somali government in the capital, Mogadishu, it is perhaps not surprising that Somali officials have been reluctant to admit that Kenyan troops have crossed the border to fight.
Another reason for disquiet among Somali officials is that Kenya has been assisting Somali efforts to establish a semi-autonomous region known as Jubaland or Azania.
The idea is that if a secure area can be established near the border, Kenya will be safer.
"The presence of foreign troops in that area will not go down well with some elements in Somalia who will not want the Azania project to be seen as a foreign initiative," said Rashid Abdi.
The fighting will of course have an impact on Somali people trying to flee their country and seek refuge in Kenya from hunger and bullets.
Already facing terrifying journeys to make it over the border, the presence of more firepower from above and on the ground will only make those journeys harder.
Last week, 800 Somalis were reaching Dadaab every day.