SANTA CLARA, Calif. (AP) Once the San Francisco 49ers got going on offense, Brock Purdy and crew once again couldn't be stopped.

Brock Purdy threw two touchdown passes and Christian McCaffrey ran for a score as the 49ers scored touchdowns on three straight second-half possessions to beat the Denver Broncos 24-14 on Sunday to remain undefeated.

Both offenses struggled to generate offense on a hot day in the Bay Area, but the 49ers (4-0) took advantage of a fumbled punt return by Marvin Mims Jr. to set up a short touchdown drive in the third quarter that gave them the lead for good.

San Francisco had been held to three points on seven possessions before the takeaway that set the stage for three straight touchdowns as the Niners took advantage of injuries that knocked out both of Denver's starting cornerbacks, including two-time All Pro Patrick Surtain II.

We wanted to break through whatever that was and just be ourselves, Purdy said. I'm glad we could get some momentum going in the second half. That's why it's a four-quarter game.

Purdy capped the 28-yard drive with a 1-yard touchdown pass to Deebo Samuel that made it 10-3 late in the third quarter. He then engineered a 74-yard drive that McCaffrey finished with a 1-yard run to extend the lead to 17-6 midway through the fourth after the Broncos (2-2) had settled for a field goal on fourth-and-2.

Bo Nix, who has thrived in late-game comeback situations, tried to mount another for Denver with his 13-yard touchdown pass to Jaylen Waddle cutting the Niners' lead to 17-14 with a 2-point conversion with 4:05 to play.

But the 49ers sealed the win when Kittle took a screen pass behind the line of scrimmage and outraced former teammate Talanoa Hufanga for a 56-yard touchdown with 2:15 to go.

Any time you see green grass, I think I ran the entire time with a smile on my face, said Kittle, who'll turn 33 on Friday. Always outrunning younger, old teammates is always a good time, especially when theyre (27).

Purdy finished 19 of 30 for 218 yards and avoided taking a sack for a fourth straight game and had no turnovers.

Nix struggled to push the ball downfield most of the game with Denver's running game unable to loosen up the defense. He finished 25 of 42 for 214 yards and one touchdown.

We just didnt have enough offense to get a lead and then go beyond that, coach Sean Payton said. We just didnt have enough answers to get past that and get a lead.

The 49ers came in scoring touchdowns on nearly half of their possessions, but struggled to move the ball against Denver's stout defense. They punted on two of their first three possessions with Purdy getting stopped on a fourth-down sneak on the other.

San Francisco got on the board with a 24-yard field goal to tie it late in the first half, but had a chance to take the lead thwarted when a field goal was blocked on the final play of the first half to keep the game tied at 3.

I think we had plays to be made," Nix said. I think as a team there were plays out there for us that needed to be made.

Injuries

Broncos: Surtain (ankle), CB Riley Moss (ribs) and WR Pat Bryant (ankle) all left with injuries and didn't return. Payton had no immediate word on the extent of the injuries.

49ers: FB Kyle Juszczyk left with a sprained knee injury after being hit by Jahdae Barron and didn't return. ... S Marques Sigle (ankle) and CB Upton Stout (shoulder) also left. Shanahan had no immediate word on the extent of the injuries.

Up next

Broncos: Visit the Los Angeles Chargers next Sunday.

49ers: Visit Seattle next Sunday.

The Defense Department will no longer appoint civilians as tenured college faculty at the United States military service academies, according to a memo signed Tuesday by Secretary Pete Hegseth.

The memo describes the decision to stop granting tenure to civilian faculty as part of an effort to refocus the military academies on warfighting.

To ensure our educational institutions remain firmly focused on this warfighting mission, we must address the structural mechanisms that have allowed civilian academic norms to dilute our focus on lethality, the memo said.

The tenure designation generally comes with a career-long academic appointment at a college. Advocates say the job security is a crucial component of academic freedom. Hegseths directive apparently would not remove the designation from faculty members who are currently tenured.

The U.S. Military Academy at West Point, the U.S. Naval Academy, and the U.S. Air Force Academy all did not immediately respond to questions, and officials at the Pentagon did not offer further details on the plan when reached for comment.

The percentage of faculty who are civilians varies by military academy. It is highest at the United States Naval Academy, where roughly half of the 600 faculty members are civilians. The academies hire civilian faculty to offer expertise in topics and disciplines that military officers dont study as part of their careers, such as English and the humanities.

Hegseths decision follows broader conservative attacks on tenured faculty appointments in higher education. Those efforts to rein in tenure are often presented as bids to rein in academics with liberal views.

Civilian faculty members often have more teaching experience and credentials than their military counterparts at the service academies, said Eric Merriam, a legal studies and political science professor at the University of Central Florida and a former professor at the Air Force Academy.

The academies have long served a dual role training the next generation of officers, while providing a traditional, prestigious, four-year college experience, Merriam said. The schools offer a broad, liberal arts education, in recognition that senior leadership must be critical thinkers who can understand different points of view.

Hegseths actions signal a shift toward a narrower focus, Merriam said.

It does seem to me as though its a retrenchment, he said. Its a retreat from what I think was positive progress in ensuring that these elite educational academies actually have elite education as part of the program.

In Hegseths memo Tuesday, tenure was described as a factor that contributed to academic stagnation, faculty complacency, and institutional inability to adapt to emerging needs. Additionally, it contributes to curriculum that drifts from the mission of educating our warfighters to the research priorities of the tenured academics.

Traditionally, tenured professors can be terminated only under extreme circumstances, such as professional misconduct or a financial emergency. Advocates say its especially important to maintain tenure as controversy grows over scholarly discussions about history, race, gender and sexuality.

The decision Tuesday is part of a broader push from Hegseth to remake the militarys education apparatus. Earlier this year, the Pentagon severed longstanding ties with prestigious universities that had been a pipeline for military leadership, forging new relationships with Christian schools and public universities.

The Pentagon has also attempted to reorient the K-12 schools it operates for military families. It introduced a course centered on Western civilization and Christianity, part of an effort to redirect the education system toward patriotic values and classical learning.

___

The Associated Press education coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find APs standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org .