diff --git a/__test__/create-or-update-branch.int.test.ts b/__test__/create-or-update-branch.int.test.ts
index 213dc8339..6d1b99af5 100644
--- a/__test__/create-or-update-branch.int.test.ts
+++ b/__test__/create-or-update-branch.int.test.ts
@@ -631,6 +631,69 @@ describe('create-or-update-branch tests', () => {
     ).toBeTruthy()
   })
 
+  it('tests create, force push of base branch, and update with identical changes', async () => {
+    // If the base branch is force pushed to a different commit when there is an open
+    // pull request, the branch must be reset to rebase the changes on the base.
+
+    // Create tracked and untracked file changes
+    const changes = await createChanges()
+    const commitMessage = uuidv4()
+    const result = await createOrUpdateBranch(
+      git,
+      commitMessage,
+      '',
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    expect(result.action).toEqual('created')
+    expect(await getFileContent(TRACKED_FILE)).toEqual(changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(changes.untracked)
+    expect(
+      await gitLogMatches([commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+
+    // Push pull request branch to remote
+    await git.push([
+      '--force-with-lease',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${BRANCH}`
+    ])
+
+    await afterTest(false)
+    await beforeTest()
+
+    // Force push the base branch to a different commit
+    const amendedCommitMessage = uuidv4()
+    await git.commit(['--amend', '-m', amendedCommitMessage])
+    await git.push([
+      '--force',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${DEFAULT_BRANCH}`
+    ])
+
+    // Create the same tracked and untracked file changes (no change on update)
+    const _changes = await createChanges(changes.tracked, changes.untracked)
+    const _commitMessage = uuidv4()
+    const _result = await createOrUpdateBranch(
+      git,
+      _commitMessage,
+      '',
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    expect(_result.action).toEqual('updated')
+    expect(_result.hasDiffWithBase).toBeTruthy()
+    expect(await getFileContent(TRACKED_FILE)).toEqual(_changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(_changes.untracked)
+    expect(
+      await gitLogMatches([_commitMessage, amendedCommitMessage])
+    ).toBeTruthy()
+  })
+
   it('tests create and update with commits on the working base (during the workflow)', async () => {
     // Create commits on the working base
     const commits = await createCommits(git)
@@ -1519,6 +1582,75 @@ describe('create-or-update-branch tests', () => {
     ).toBeTruthy()
   })
 
+  it('tests create, force push of base branch, and update with identical changes (WBNB)', async () => {
+    // If the base branch is force pushed to a different commit when there is an open
+    // pull request, the branch must be reset to rebase the changes on the base.
+
+    // Set the working base to a branch that is not the pull request base
+    await git.checkout(NOT_BASE_BRANCH)
+
+    // Create tracked and untracked file changes
+    const changes = await createChanges()
+    const commitMessage = uuidv4()
+    const result = await createOrUpdateBranch(
+      git,
+      commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    expect(result.action).toEqual('created')
+    expect(await getFileContent(TRACKED_FILE)).toEqual(changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(changes.untracked)
+    expect(
+      await gitLogMatches([commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+
+    // Push pull request branch to remote
+    await git.push([
+      '--force-with-lease',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${BRANCH}`
+    ])
+
+    await afterTest(false)
+    await beforeTest()
+
+    // Force push the base branch to a different commit
+    const amendedCommitMessage = uuidv4()
+    await git.commit(['--amend', '-m', amendedCommitMessage])
+    await git.push([
+      '--force',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${DEFAULT_BRANCH}`
+    ])
+
+    // Set the working base to a branch that is not the pull request base
+    await git.checkout(NOT_BASE_BRANCH)
+
+    // Create the same tracked and untracked file changes (no change on update)
+    const _changes = await createChanges(changes.tracked, changes.untracked)
+    const _commitMessage = uuidv4()
+    const _result = await createOrUpdateBranch(
+      git,
+      _commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    expect(_result.action).toEqual('updated')
+    expect(_result.hasDiffWithBase).toBeTruthy()
+    expect(await getFileContent(TRACKED_FILE)).toEqual(_changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(_changes.untracked)
+    expect(
+      await gitLogMatches([_commitMessage, amendedCommitMessage])
+    ).toBeTruthy()
+  })
+
   it('tests create and update with commits on the working base (during the workflow) (WBNB)', async () => {
     // Set the working base to a branch that is not the pull request base
     await git.checkout(NOT_BASE_BRANCH)
diff --git a/dist/index.js b/dist/index.js
index 23b649f32..81ec93919 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -74,18 +74,30 @@ function tryFetch(git, remote, branch) {
     });
 }
 exports.tryFetch = tryFetch;
+// Return the number of commits that branch2 is ahead of branch1
+function commitsAhead(git, branch1, branch2) {
+    return __awaiter(this, void 0, void 0, function* () {
+        const result = yield git.revList([`${branch1}...${branch2}`], ['--right-only', '--count']);
+        return Number(result);
+    });
+}
 // Return true if branch2 is ahead of branch1
 function isAhead(git, branch1, branch2) {
     return __awaiter(this, void 0, void 0, function* () {
-        const result = yield git.revList([`${branch1}...${branch2}`], ['--right-only', '--count']);
-        return Number(result) > 0;
+        return (yield commitsAhead(git, branch1, branch2)) > 0;
+    });
+}
+// Return the number of commits that branch2 is behind branch1
+function commitsBehind(git, branch1, branch2) {
+    return __awaiter(this, void 0, void 0, function* () {
+        const result = yield git.revList([`${branch1}...${branch2}`], ['--left-only', '--count']);
+        return Number(result);
     });
 }
 // Return true if branch2 is behind branch1
 function isBehind(git, branch1, branch2) {
     return __awaiter(this, void 0, void 0, function* () {
-        const result = yield git.revList([`${branch1}...${branch2}`], ['--left-only', '--count']);
-        return Number(result) > 0;
+        return (yield commitsBehind(git, branch1, branch2)) > 0;
     });
 }
 // Return true if branch2 is even with branch1
@@ -214,9 +226,16 @@ function createOrUpdateBranch(git, commitMessage, base, branch, branchRemoteName
             //   branches after merging. In particular, it catches a case where the branch was
             //   squash merged but not deleted. We need to reset to make sure it doesn't appear
             //   to have a diff with the base due to different commits for the same changes.
+            // - If the number of commits ahead of the base branch differs between the branch and
+            //   temp branch. This catches a case where the base branch has been force pushed to
+            //   a new commit.
             // For changes on base this reset is equivalent to a rebase of the pull request branch.
+            const tempBranchCommitsAhead = yield commitsAhead(git, base, tempBranch);
+            const branchCommitsAhead = yield commitsAhead(git, base, branch);
             if ((yield git.hasDiff([`${branch}..${tempBranch}`])) ||
-                !(yield isAhead(git, base, tempBranch))) {
+                branchCommitsAhead != tempBranchCommitsAhead ||
+                !(tempBranchCommitsAhead > 0) // !isAhead
+            ) {
                 core.info(`Resetting '${branch}'`);
                 // Alternatively, git switch -C branch tempBranch
                 yield git.checkout(branch, tempBranch);
diff --git a/src/create-or-update-branch.ts b/src/create-or-update-branch.ts
index 7dcd9fcdf..ebdef12cd 100644
--- a/src/create-or-update-branch.ts
+++ b/src/create-or-update-branch.ts
@@ -43,30 +43,48 @@ export async function tryFetch(
   }
 }
 
-// Return true if branch2 is ahead of branch1
-async function isAhead(
+// Return the number of commits that branch2 is ahead of branch1
+async function commitsAhead(
   git: GitCommandManager,
   branch1: string,
   branch2: string
-): Promise<boolean> {
+): Promise<number> {
   const result = await git.revList(
     [`${branch1}...${branch2}`],
     ['--right-only', '--count']
   )
-  return Number(result) > 0
+  return Number(result)
 }
 
-// Return true if branch2 is behind branch1
-async function isBehind(
+// Return true if branch2 is ahead of branch1
+async function isAhead(
   git: GitCommandManager,
   branch1: string,
   branch2: string
 ): Promise<boolean> {
+  return (await commitsAhead(git, branch1, branch2)) > 0
+}
+
+// Return the number of commits that branch2 is behind branch1
+async function commitsBehind(
+  git: GitCommandManager,
+  branch1: string,
+  branch2: string
+): Promise<number> {
   const result = await git.revList(
     [`${branch1}...${branch2}`],
     ['--left-only', '--count']
   )
-  return Number(result) > 0
+  return Number(result)
+}
+
+// Return true if branch2 is behind branch1
+async function isBehind(
+  git: GitCommandManager,
+  branch1: string,
+  branch2: string
+): Promise<boolean> {
+  return (await commitsBehind(git, branch1, branch2)) > 0
 }
 
 // Return true if branch2 is even with branch1
@@ -226,10 +244,16 @@ export async function createOrUpdateBranch(
     //   branches after merging. In particular, it catches a case where the branch was
     //   squash merged but not deleted. We need to reset to make sure it doesn't appear
     //   to have a diff with the base due to different commits for the same changes.
+    // - If the number of commits ahead of the base branch differs between the branch and
+    //   temp branch. This catches a case where the base branch has been force pushed to
+    //   a new commit.
     // For changes on base this reset is equivalent to a rebase of the pull request branch.
+    const tempBranchCommitsAhead = await commitsAhead(git, base, tempBranch)
+    const branchCommitsAhead = await commitsAhead(git, base, branch)
     if (
       (await git.hasDiff([`${branch}..${tempBranch}`])) ||
-      !(await isAhead(git, base, tempBranch))
+      branchCommitsAhead != tempBranchCommitsAhead ||
+      !(tempBranchCommitsAhead > 0) // !isAhead
     ) {
       core.info(`Resetting '${branch}'`)
       // Alternatively, git switch -C branch tempBranch