Six soldiers in full combat gear ascend a spiral staircase, their SAR 21 assault rifles at the ready.
As they approach a closed door, the leader of the group moves silently to cover the front, while another two take up position at the left and right, using hand signals and visual cues to coordinate their entry.
When ready, they burst into the room and open fire - only this time, they are training rounds.
The Singapore Armed Forces' 1st Commando Battalion gave The Straits Times a glimpse into urban operation techniques during a recent training session.
And it was this kind of expertise that helped the elite group of soldiers win the Best Combat Unit title for the 13th time in a row this year.
Their win also makes it the 30th time the battalion has won the title since the competition began in 1969. The awards, spanning 25 categories, will be handed out tomorrow, which is also SAF Day. And units are ranked according to several stringent criteria in the annual contest.
Lieutenant-Colonel Alvin Tjioe, the commanding officer of the 1st Commando Battalion, said the unit fights for the award every year.
"What a lot of people might not realise is that, every year, when we go through the Best Unit Competition, the soldiers are doing it for the first time," he said. Full-time national serviceman graduate from the unit after their two-year-stint is over.
"The challenge is to make sure that lots of good practices are retained and passed down to the next command team, and that they are built upon year after year," added LTC Tjioe.
Aside from active units, units comprising operationally ready national servicemen are also awarded the Best Unit title.
The 3rd Combat Support Hospital, which specialises in field medical support and surgery, was awarded the title of Best NS Combat Service Support Unit this year.
As an NS unit working behind the frontlines, the challenges it faces are different from those faced by an active frontline unit.
Its commanding officer LTC (NS) David Ng said: "These are highly educated guys. They come in for two weeks but for the rest of the year, they are out there as professionals. It's a sacrifice for them.
"For an NS unit, we must always remember the families and employers of the men. For an NS unit, in contrast to an active unit, these things are very important."
LTC Tjioe said ultimately though, the title of Best Unit is not the "be all and end all of good performance". "Ultimately, the end goal is to be the best units we can be so that we can continue to keep Singapore safe."
The Best Unit award takes into account several factors, including the unit's participation rate in operations and exercises, training safety standards, soldiers' Individual Physical Proficiency Test performances, and proficiency in the units' respective vocations.
Eighteen active and 11 NS units will be recognised as Best Units at the SAF Day Parade tomorrow.
Some of the winners include the 3rd Battalion Singapore Guards, which has been awarded the Best Infantry/Guards Unit of the Army.
The RSS Vigour is this year's Best Fleet Unit of the Navy, and 140 Squadron is the Best Fighter Squadron of the Air Force.