The first troops from a contingent of Japanese forces sent to Iraq have crossed the border from Kuwait.
A small vanguard is already in Samawah to prepare for the deployment
The group of several dozen are the first Japanese soldiers to be deployed in a combat zone since World War II.
Their mission is purely humanitarian, but critics in Japan have argued that their deployment is a violation of the country's pacifist constitution.
The troops are part of a contingent of 600 who will be based in the southern Iraqi city of Samawah.
The group arrived at a military checkpoint in Iraq at 0820 local time (0520 GMT) in a convoy of 25 trucks.
"Let's do the work that makes history," unit commander Colonel Yasushi Kiyota was quoted as saying. "Do your work as usual."
Opposition at home
The troops had been in Kuwait since the approval of the lower house of parliament at the end of January.
They will join a small number of reconnaissance troops already in Iraq.
The rest of the main contingent will leave Japan for Iraq later in February.
Opinion polls suggest that about half of the Japanese public is currently opposed to the deployment.
Japan's constitution prohibits the use of force in international disputes, but the Japanese Government argues the country is entitled to exercise self-defence and the troops will be able to return fire if they are attacked.
Prime Minister Junichiro Koizumi has argued that the mission is necessary to bolster Japan's role in the international community.