"It was survival," he said.
Lohse limited the Nationals to one run over seven innings despite giving up 10 hits and allowing at least one base runner in every inning.
"I think it was five out of seven innings that got led off with a hit. I was thinking about starting off innings out of the stretch, but I didn't want to let everybody know I was aware of it," Lohse joked.
Aramis Ramirez added a two-run single for the NL Central leading Brewers.
Lohse (10-4) picked up his first win since June 22 as Washington went 1 for 10 with runners in scoring position.
"That's being able to make pitches and battle when you're not completely on your game," Brewers manager Ron Roenicke said.
Lohse threw 103 pitches. He struck out three without a walk
Milwaukee shortstop Jean Segura was back in the lineup, a week after the death of his 9-month-old son, and went 1 for 4. He received a warm ovation from the Nationals Park crowd prior to his first at-bat.
"It was amazing, you know, it was amazing," Segura said of the acknowledgement. "When a player has that experience, (is in) that position, it's tough. They know how difficult this game is and how hard we go out there and compete"
Bryce Harper, struggling since returning from a left thumb injury had a homer and two singles for Washington, which began play percentage points ahead of Atlanta in the NL East.
"I think he's stood up just a touch more to get on top of the baseball. Lowered his hands a little bit, probably a little more direct to the ball. He worked on that over the break," manager Matt Williams said. "He looked good up there tonight."
Francisco Rodriguez gave up Harper's ninth-inning homer, but picked up his 28th save.
Stephen Strasburg (7-7) allowed four runs on seven hits. He struck out nine in seven innings.
Washington had won 10 of 14 coming in while the Brewers had dropped 11 of 13, but it was Milwaukee that started fast.
The Brewers got solo homers from Gennett in the first inning and Davis in the second.
In the fourth, Strasburg issued a two-out walk to Gennett and Ryan Braun doubled him to third. Ramirez then blooped a single, scoring both runners to make it 4-0.
"I got in off Ramirez's hands hard and he just dumped it out there in right," Strasburg said. "That was the one that was really frustrating."
Strasburg, who allowed seven runs in 4 2-3 innings June 25 in Milwaukee, had given up just five earned runs in 20 1-3 innings in his three starts since.
The Nationals pulled to within 4-1 on Ian Desmond's RBI double.
An obstruction call briefly delayed the first inning.
Span beat the throw to second and was initially called safe, and second baseman Gennett's relay throw got Rendon at first. However, second base umpire Angel Campos called Span out for obstruction as Span came up into Gennett after his slide.
Williams argued and the umpires huddled.
Span remained out but Rendon was ruled safe at first because Span's obstruction created a dead-ball situation.
"I think they got it wrong, but I can't tell you the ruling on it because I've never seen it before," Roenicke said. "(Crew Chief Bill Miller) said once the umpire calls him safe and then calls the interference it becomes a dead ball."
Segura had gone back to the Dominican Republic after the death of his son, Janniel, last Friday, and rejoined the team Thursday. ... Williams said RHP Jordan Zimmermann, who left his last start in the fourth inning due to a right biceps cramp, will pitch a bullpen session Saturday and is tentatively scheduled to start Tuesday at Colorado. ... RHP Tanner Roark (8-6, 3.01) will pitch Saturday against Milwaukee's Matt Garza (6-6, 3.69). LHP Gio Gonzalez had been scheduled to pitch for Washington, but missed Thursday's team workout -- and his bullpen session -- when one of his flights was cancelled, according to Williams. Gonzalez threw a bullpen session Friday and will pitch Sunday. ... The Nationals announced they have agreed to terms with right-hander Erick Fedde, the 18th overall pick in the 2014 draft.