THE FIRST JAPANESE TROOPS DEPLOYED TO A COMBAT ZONE SINCE WORLD WAR II MARKED THE END OF THEIR MISSION SATURDAY BY CELEBRATING THE RETURN OF THE ARMY FLAG THAT FLEW OVER THEM FOR 2 1/2 YEARS IN IRAQ. ABOUT 1,000 RECENTLY RETURNED SOLDIERS AND WELL-WISHERS ATTENDED A CEREMONY AT ASAKA TRAINING GROUND NORTH OF TOKYO, THAT ALSO INCLUDED JAPANESE PRIME MINISTER JUNICHIRO KOIZUMI AND IRAQ'S AMBASSADOR TO JAPAN GHANIM ALWAN AL-JUMAILY. «THE TROOPS DID AN ADMIRABLE JOB IN THE MOST DIFFICULT OF CONDITIONS,» KOIZUMI TOLD THE CROWD. «THIS MISSION WILL REMAIN IN THE MEMORIES OF BOTH THE JAPANESE AND IRAQI PEOPLE.» COL. TOSHIHIRO YAMANAKA, WHO LED JAPAN'S FINAL CONTINGENT TO IRAQ, CAREFULLY HANDED DEFENSE CHIEF FUKUSHIRO NUKAGA THE FLAG THAT FLEW OVER JAPAN'S BASE IN THE SOUTHERN IRAQI CITY OF SAMAWAH. «I AM RELIEVED TO HAVE BROUGHT THE FLAG BACK SAFELY,» SAID YAMANAKA. A TOTAL OF 5,500 TROOPS WERE DEPLOYED TO IRAQ DURING THE 2 1/2-YEAR MISSION, HE WAS QUOTED AS SAYING BY THE ASSOCIATED PRESS.