[Written for prompt by WattpadMilitaryFiction  . Word count – 1000 words]

The SONAR system blinked to life as the crew members huddled around the screen, their cautious gaze alternating between the blinking warning and the aqueous expanse around the submarine which the periscope offered a view of.

"You're certain it's not one of our own?" Samal Mizrahi questioned the Sonar Operator who had just descended from the periscope. The man shook his head at the lieutenant.

"I don't recognise the vessel, Samal. It's a German model, that's all we can conclude."

"If it's not our own, we have a potential enemy vessel approaching our national waters," Shira spoke up, walking upto the blinking screen. The SONAR system had locked in on the unknown vessel, which appeared roughly the same size as their own Dolphin-class submarine.

"Egyptians?" Shira ventured, earning a non-committed tilt of the head from Samal Mizrahi.

"We're too deep underwater to establish communication with Base," Mizrahi stated, turning back to the naval personnel in the vessel.

"I suggest we ascend to Base and report the rogue submarine approaching our national waters."

Sticking to protocol, I see.

Shira let a moment of silence elapse after the lieutanent's words before voicing her thoughts.

"Samal, the rogue vessel is closer to our national waters than we are to Base," Captain Kaganov replied.

"By the time we ascend and launch a counterstrike, the enemy would be well into our territory. The Dolphin is equipped for situations like this. I suggest we advance, threatening a use of force. Failure on the enemy's part to retreat will be followed up with our torpedos."

"Katzin Kaganov," Mizrahi addressed the captain, his words reflecting his protest.

"I don't believe it's wise to attack a rogue submarine unless it's breached our territory! The Defenders will launch strikes against them if they enter. Besides, it's our duty as a surveillance team to alert Base of all anomalies-"

"I'm well aware of your duty, Samal Mizrahi," Shira responded sharply. Her eyes travelled back to the glowing screen, where the green dot of the unidentified submarine was inching closer towards their underwater border.

'Unidentified' would have been inaccurate, given that Shira had recognised the vessel the moment she saw it.  The pretence, however, would have to continue.

"There's no telling how much ammunition the vessel is equipped with," Captain Kaganov added.

"The northern front Defender may be overpowered, in which case this rogue vessel will have access to two kilometres of our territory. Enough to occupy and clear for allied vessels."

Mizrahi took his hands off the controls, allowing the Dolphin submarine to glide through the inky darkness, maintaining a steady pace behind the enemy. The Dolphin's acoustic camouflage mechanism had been switched on before the surveillance operation had begun, and it had served its purpose well.

The rogue hadn't been alerted of the Israeli vessel tailing it; if it had, it certainly kept up the pretence.

Shira's eyes skimmed the bathymetric chart that the crew had unrolled on the work table. The underwater trench that they carefully maneuvered through on every drill loomed ahead of the submarine. Deploying a torpedo in that claustrophobic crevice would significantly damage the vessel ahead of them, but damage to their own hull was a risk the crew couldn't rule out.

Captain Kaganov strode upto the submarine control panel and let the Dolphin swerve gently to the left, passing through a herd of what appeared to be dugongs.

Deploy a torpedo that kills a dozen of these endangered manatees and the international community will have our skin.

Shira smirked to herself. Still, it was worth the suggestion if it elicited the response from the samal that she was looking for.

The submarine had cleared the trench and emerged on the other side. Mizrahi frowned at the SONAR system, which had, for a second, stopped tracing the rogue submarine's signal.

The green dot now reappeared less than a mile eastward, indicating the other submarine's quickened pace. The national border would come into sight soon, and the crew had yet to make a decision.

"Pick up the pace, Samal," Kaganov instructed. "Prepare for Strike One, starboard torpedo."

Lieutenant Mizrahi gritted his teeth as he steered the vessel eastward, accelerating to meet the pace of the rogue.

In the absence of his own captain, Katzin Azulay, Mizrahi was not keen on obeying the orders of a captain from another unit altogether. The conflict in his mind had become apparent ages ago.

A captain from a psychological warfare branch... What do you know of underwater defence?

"Katzin Kaganov, in the absence of Katzin Azulay, I'm afraid we must follow protocol," the lieutanent stated. The crew looked on as the lieutanent was met with a frigid look from the captain.

"That vessel will be at our doorstep in a minute, Samal," Kaganov replied flatly.

"Code 12 calls for attack when in doubt, and this is one of those occasions."

Offence is the best form of defence. Take the bait, Mizrahi, Shira advised silently.

The rhythmic beeping of the SONAR alerted the crew of the rogue submarine alarmingly close to their national waters. This was it –
The lieutanent's call would determine it all, although Shira was certain that Mizrahi wasn't fully aware of what was on the line.

Samal Mizrahi took a deep breath, before turning to Shira.

"I'm sorry, Katzin Kaganov. We were trained differently by Katzin Azulay." 

All doubt evaporated from his mind as Mizrahi commanded his crew to prepare for ascent. They complied, leaving Captain Kaganov to herself.

Shira impassively regarded the soldiers who had been jerked into action, before exiting to the crew bunkers quietly. Opening her locker, she withdrew a notebook and quickly began scrawling in it as the submarine lurched upward.

"Calm during stress. Sticks to protocol. Does not take empty advice from senior officers, despite their being of higher rank. Loyal to own captain, mistrusting of newcomers."

The entire surveillance crew, especially Samal Mizrahi, didn't need to know that Shira was there in her capacity as a military psychologist, not a captain.