Then Sgt. Eric Garcia's phone pinged with a notification. He and the driver follow each other on Snapchat. So the soldier sent a photo to Garcia with instructions to call.
Garcia and the other soldiers, their boots soaked in floodwater, couldn't help but laugh at potentially the first-ever military vehicle recovery with a photo-sharing app.
As the entire Texas National Guard mobilized to save civilians in the still-churning waters of Hurricane Harvey's aftermath this week, the episode illuminated digital tech's key role in how soldiers here execute relief missions.
Guard soldiers from the San Antonio-based 71st Expeditionary Intelligence Military Brigade used group texts and smartphone calls to coordinate, which was often the best way to disseminate instant information when distance over the sprawling Houston suburb made traditional radio communication difficult.
The mission began with a briefing: Each of the six vehicles heading out would have a Texas Department of Public Safety officer in tow and separately patrol ravaged neighborhoods to deter looters and pluck civilians from danger. National Guard officials have stressed that civil authorities have the lead in Harvey rescue and relief efforts, with military units in support.
But one soldier said the officer in his vehicle was told the opposite - that Guard soldiers were the lead authority. The officer did not have a map or any suggestions of where to go, expecting the soldiers, many of whom lived hours away in San Antonio and did not know the area well, to assemble intelligence and patrol routes.
"Coordination gets lost in translation as it trickles down," Garcia said, echoing a timeless soldier complaint of orders frayed at every echelon, from the governor of Texas all the way down to a 19-year-old private behind the wheel of an armored vehicle.
Radios can be limited by range without powerful retransmission towers, but they have one big advantage over cellphones - they're powered by the vehicle. And Humvees don't have USB ports.
Garcia and the mechanic in his Humvee, Sgt. Jason Cameron, 27, watched their batteries slowly drain as their vehicle lumbered through suburban enclaves.
Some people got out of their cars near high-water areas to take photos with their phones. At a distance, they appeared to be in distress.
"It definitely gets confusing when they're out there taking photos. It takes away from our time and mission," Garcia said. "Those seconds or minutes could be the difference. But I guess it's not every day you see an up-armored Humvee in your neighborhood."
In the late afternoon, the officer aboard Garcia's vehicle relayed an address that was reported the day before to be in danger of flooding. Garcia sped to the location as Cameron's smartphone GPS squawked directions.
Garcia pulled up to a dry home. Cameron got out to knock on the door. No answer. Onlookers admired the Humvee as Cameron turned to walk back.
"Hey!" a woman said as she opened the door, surprised to see a soldier in her driveway. She explained that the water nearly reached the sidewalk but later receded.
Back to the basics
By nightfall, most of the cellphones in the group neared zero percent battery life.
"It's a learning-curve moment. Maybe next time we roll out we'll have consistent radio communication, just like in-country," he said, referring to his deployment to Iraq in 2008. "If your communications go bad there, you're inoperable."
Some soldiers found creative ways to harness social media. A soldier on a separate mission said Facebook became a vital tool for civilians to report precise locations of trapped people, and a responding unit located and rescued dozens from a building that way.
"Hats off to Google Maps and dropping pins on iPhone," he said.
Garcia's group had one more mission near midnight. A report from the police said high floodwaters were endangering civilians in east Houston. This time the radios powered on.
"We need a refresher course on GOTWA," Garcia said, referring to a military acronym used to plan contingencies when leaders are absent. He illuminated the radio with his iPhone to finish programming the frequency.
"Hell, we need a beginner's course on GOTWA," Cameron shot back as he leaned into the truck and bit at a plug of chewing tobacco.
The clicks and pops of radio checks streamed between the vehicles, a familiar noise in combat. The unit linked up with officers and civilian volunteer rescuers in boats readying for a wall of water. Garcia's unit even brought high-water vehicles in case it became too treacherous for Humvees.
But the mission to eastern Houston was a literal dry hole - the neighborhood wasn't under threat any longer. The convoy headed back to base as the mayor-imposed curfew settled in.
The lead vehicle missed an exit and got onto a toll road, forcing the convoy to detour and loop back around. A Humvee approached a toll booth, and the vehicle commander keyed the radio.
"Anyone got exact change?" he asked.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)