diff --git a/vault/activity_log.go b/vault/activity_log.go
index 8d11a7ab5..221ad5c8b 100644
--- a/vault/activity_log.go
+++ b/vault/activity_log.go
@@ -409,67 +409,82 @@ func (a *ActivityLog) saveCurrentSegmentToStorageLocked(ctx context.Context, for
 
 // :force: forces a save of tokens/entities even if the in-memory log is empty
 func (a *ActivityLog) saveCurrentSegmentInternal(ctx context.Context, force bool) error {
-	entityPath := fmt.Sprintf("%s%d/%d", activityEntityBasePath, a.currentSegment.startTimestamp, a.currentSegment.clientSequenceNumber)
+	_, err := a.saveSegmentEntitiesInternal(ctx, a.currentSegment, force)
+	if err != nil {
+		return err
+	}
+	_, err = a.saveSegmentTokensInternal(ctx, a.currentSegment, force)
+	return err
+}
+
+func (a *ActivityLog) saveSegmentTokensInternal(ctx context.Context, currentSegment segmentInfo, force bool) (string, error) {
+	if len(currentSegment.tokenCount.CountByNamespaceID) == 0 && !force {
+		return "", nil
+	}
 	// RFC (VLT-120) defines this as 1-indexed, but it should be 0-indexed
-	tokenPath := fmt.Sprintf("%s%d/0", activityTokenBasePath, a.currentSegment.startTimestamp)
+	tokenPath := fmt.Sprintf("%s%d/0", activityTokenBasePath, currentSegment.startTimestamp)
+	// We must still allow for the tokenCount of the current segment to
+	// be written to storage, since if we remove this code we will incur
+	// data loss for one segment's worth of TWEs.
+	// We can get away with simply using the oldest version stored because
+	// the storing of versions was introduced at the same time as this code.
+	oldestVersion, oldestUpgradeTime, err := a.core.FindOldestVersionTimestamp()
+	switch {
+	case err != nil:
+		a.logger.Error(fmt.Sprintf("unable to retrieve oldest version timestamp: %s", err.Error()))
+	case len(a.currentSegment.tokenCount.CountByNamespaceID) > 0 &&
+		(oldestUpgradeTime.Add(time.Duration(trackedTWESegmentPeriod * time.Hour)).Before(time.Now())):
+		a.logger.Error(fmt.Sprintf("storing nonzero token count over a month after vault was upgraded to %s", oldestVersion))
+	default:
+		if len(a.currentSegment.tokenCount.CountByNamespaceID) > 0 {
+			a.logger.Info("storing nonzero token count")
+		}
+	}
+	tokenCount, err := proto.Marshal(a.currentSegment.tokenCount)
+	if err != nil {
+		return "", err
+	}
+
+	a.logger.Trace("writing segment", "path", tokenPath)
+	err = a.view.Put(ctx, &logical.StorageEntry{
+		Key:   tokenPath,
+		Value: tokenCount,
+	})
+	if err != nil {
+		return "", err
+	}
+
+	return tokenPath, nil
+}
+
+func (a *ActivityLog) saveSegmentEntitiesInternal(ctx context.Context, currentSegment segmentInfo, force bool) (string, error) {
+	entityPath := fmt.Sprintf("%s%d/%d", activityEntityBasePath, currentSegment.startTimestamp, currentSegment.clientSequenceNumber)
 
 	for _, client := range a.currentSegment.currentClients.Clients {
 		// Explicitly catch and throw clear error message if client ID creation and storage
 		// results in a []byte that doesn't assert into a valid string.
 		if !utf8.ValidString(client.ClientID) {
-			return fmt.Errorf("client ID %q is not a valid string:", client.ClientID)
+			return "", fmt.Errorf("client ID %q is not a valid string:", client.ClientID)
 		}
 	}
 
-	if len(a.currentSegment.currentClients.Clients) > 0 || force {
-		clients, err := proto.Marshal(a.currentSegment.currentClients)
-		if err != nil {
-			return err
-		}
-
-		a.logger.Trace("writing segment", "path", entityPath)
-		err = a.view.Put(ctx, &logical.StorageEntry{
-			Key:   entityPath,
-			Value: clients,
-		})
-		if err != nil {
-			return err
-		}
+	if len(currentSegment.currentClients.Clients) == 0 && !force {
+		return "", nil
+	}
+	clients, err := proto.Marshal(currentSegment.currentClients)
+	if err != nil {
+		return entityPath, err
 	}
 
-	// We must still allow for the tokenCount of the current segment to
-	// be written to storage, since if we remove this code we will incur
-	// data loss for one segment's worth of TWEs.
-	if len(a.currentSegment.tokenCount.CountByNamespaceID) > 0 || force {
-		// We can get away with simply using the oldest version stored because
-		// the storing of versions was introduced at the same time as this code.
-		oldestVersion, oldestUpgradeTime, err := a.core.FindOldestVersionTimestamp()
-		switch {
-		case err != nil:
-			a.logger.Error(fmt.Sprintf("unable to retrieve oldest version timestamp: %s", err.Error()))
-		case len(a.currentSegment.tokenCount.CountByNamespaceID) > 0 &&
-			(oldestUpgradeTime.Add(time.Duration(trackedTWESegmentPeriod * time.Hour)).Before(a.clock.Now())):
-			a.logger.Error(fmt.Sprintf("storing nonzero token count over a month after vault was upgraded to %s", oldestVersion))
-		default:
-			if len(a.currentSegment.tokenCount.CountByNamespaceID) > 0 {
-				a.logger.Info("storing nonzero token count")
-			}
-		}
-		tokenCount, err := proto.Marshal(a.currentSegment.tokenCount)
-		if err != nil {
-			return err
-		}
-
-		a.logger.Trace("writing segment", "path", tokenPath)
-		err = a.view.Put(ctx, &logical.StorageEntry{
-			Key:   tokenPath,
-			Value: tokenCount,
-		})
-		if err != nil {
-			return err
-		}
+	a.logger.Trace("writing segment", "path", entityPath)
+	err = a.view.Put(ctx, &logical.StorageEntry{
+		Key:   entityPath,
+		Value: clients,
+	})
+	if err != nil {
+		return "", err
 	}
-	return nil
+	return entityPath, err
 }
 
 // parseSegmentNumberFromPath returns the segment number from a path
diff --git a/vault/logical_system_activity_write_testonly.go b/vault/logical_system_activity_write_testonly.go
index c1a67b8dd..45c055e1e 100644
--- a/vault/logical_system_activity_write_testonly.go
+++ b/vault/logical_system_activity_write_testonly.go
@@ -8,9 +8,12 @@ package vault
 import (
 	"context"
 	"fmt"
+	"sync"
+	"time"
 
 	"github.com/hashicorp/go-uuid"
 	"github.com/hashicorp/vault/helper/namespace"
+	"github.com/hashicorp/vault/helper/timeutil"
 	"github.com/hashicorp/vault/sdk/framework"
 	"github.com/hashicorp/vault/sdk/logical"
 	"github.com/hashicorp/vault/vault/activity"
@@ -53,7 +56,34 @@ func (b *SystemBackend) handleActivityWriteData(ctx context.Context, request *lo
 	if len(input.Data) == 0 {
 		return logical.ErrorResponse("Missing required \"data\" values"), logical.ErrInvalidRequest
 	}
-	return nil, nil
+
+	numMonths := 0
+	for _, month := range input.Data {
+		if int(month.GetMonthsAgo()) > numMonths {
+			numMonths = int(month.GetMonthsAgo())
+		}
+	}
+	generated := newMultipleMonthsActivityClients(numMonths + 1)
+	for _, month := range input.Data {
+		err := generated.processMonth(ctx, b.Core, month)
+		if err != nil {
+			return logical.ErrorResponse("failed to process data for month %d", month.GetMonthsAgo()), err
+		}
+	}
+
+	opts := make(map[generation.WriteOptions]struct{}, len(input.Write))
+	for _, opt := range input.Write {
+		opts[opt] = struct{}{}
+	}
+	paths, err := generated.write(ctx, opts, b.Core.activityLog)
+	if err != nil {
+		return logical.ErrorResponse("failed to write data"), err
+	}
+	return &logical.Response{
+		Data: map[string]interface{}{
+			"paths": paths,
+		},
+	}, nil
 }
 
 // singleMonthActivityClients holds a single month's client IDs, in the order they were seen
@@ -287,6 +317,47 @@ func (m *multipleMonthsActivityClients) addRepeatedClients(monthsAgo int32, c *g
 	return nil
 }
 
+func (m *multipleMonthsActivityClients) write(ctx context.Context, opts map[generation.WriteOptions]struct{}, activityLog *ActivityLog) ([]string, error) {
+	now := timeutil.StartOfMonth(time.Now().UTC())
+	paths := []string{}
+	for i, month := range m.months {
+		var timestamp time.Time
+		if i > 0 {
+			timestamp = timeutil.StartOfMonth(timeutil.MonthsPreviousTo(i, now))
+		} else {
+			timestamp = now
+		}
+		segments, err := month.populateSegments()
+		if err != nil {
+			return nil, err
+		}
+		for segmentIndex, segment := range segments {
+			if _, ok := opts[generation.WriteOptions_WRITE_ENTITIES]; ok {
+				if segment == nil {
+					// skip the index
+					continue
+				}
+				entityPath, err := activityLog.saveSegmentEntitiesInternal(ctx, segmentInfo{
+					startTimestamp:       timestamp.Unix(),
+					currentClients:       &activity.EntityActivityLog{Clients: segment},
+					clientSequenceNumber: uint64(segmentIndex),
+					tokenCount:           &activity.TokenCount{},
+				}, true)
+				if err != nil {
+					return nil, err
+				}
+				paths = append(paths, entityPath)
+			}
+		}
+	}
+	wg := sync.WaitGroup{}
+	err := activityLog.refreshFromStoredLog(ctx, &wg, now)
+	if err != nil {
+		return nil, err
+	}
+	return paths, nil
+}
+
 func newMultipleMonthsActivityClients(numberOfMonths int) *multipleMonthsActivityClients {
 	m := &multipleMonthsActivityClients{
 		months: make([]*singleMonthActivityClients, numberOfMonths),
diff --git a/vault/logical_system_activity_write_testonly_test.go b/vault/logical_system_activity_write_testonly_test.go
index f72a0e167..b9b1a939a 100644
--- a/vault/logical_system_activity_write_testonly_test.go
+++ b/vault/logical_system_activity_write_testonly_test.go
@@ -7,6 +7,7 @@ package vault
 
 import (
 	"context"
+	"sort"
 	"testing"
 
 	"github.com/hashicorp/vault/helper/namespace"
@@ -14,6 +15,8 @@ import (
 	"github.com/hashicorp/vault/vault/activity"
 	"github.com/hashicorp/vault/vault/activity/generation"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/encoding/protojson"
+	"google.golang.org/protobuf/proto"
 )
 
 // TestSystemBackend_handleActivityWriteData calls the activity log write endpoint and confirms that the inputs are
@@ -24,6 +27,7 @@ func TestSystemBackend_handleActivityWriteData(t *testing.T) {
 		operation logical.Operation
 		input     map[string]interface{}
 		wantError error
+		wantPaths int
 	}{
 		{
 			name:      "read fails",
@@ -70,6 +74,12 @@ func TestSystemBackend_handleActivityWriteData(t *testing.T) {
 			operation: logical.CreateOperation,
 			input:     map[string]interface{}{"input": `{"write":["WRITE_PRECOMPUTED_QUERIES"],"data":[{"current_month":true,"all":{"clients":[{"count":5}]}}]}`},
 		},
+		{
+			name:      "entities with multiple segments",
+			operation: logical.CreateOperation,
+			input:     map[string]interface{}{"input": `{"write":["WRITE_ENTITIES"],"data":[{"current_month":true,"num_segments":3,"all":{"clients":[{"count":5}]}}]}`},
+			wantPaths: 3,
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -81,6 +91,8 @@ func TestSystemBackend_handleActivityWriteData(t *testing.T) {
 				require.Equal(t, tc.wantError, err, resp.Error())
 			} else {
 				require.NoError(t, err)
+				paths := resp.Data["paths"].([]string)
+				require.Len(t, paths, tc.wantPaths)
 			}
 		})
 	}
@@ -428,3 +440,137 @@ func Test_singleMonthActivityClients_populateSegments(t *testing.T) {
 		})
 	}
 }
+
+// Test_multipleMonthsActivityClients_write_entities writes 4 months of data
+// splitting some months across segments and using empty segments and skipped
+// segments. Entities are written and then storage is queried. The test verifies
+// that the correct timestamps are present in the activity log and that the correct
+// segment numbers for each month contain the correct number of clients
+func Test_multipleMonthsActivityClients_write_entities(t *testing.T) {
+	index5 := int32(5)
+	index4 := int32(4)
+	data := &generation.ActivityLogMockInput{
+		Write: []generation.WriteOptions{
+			generation.WriteOptions_WRITE_ENTITIES,
+		},
+		Data: []*generation.Data{
+			{
+				// segments: 0:[x,y], 1:[z]
+				Month:       &generation.Data_MonthsAgo{MonthsAgo: 3},
+				Clients:     &generation.Data_All{All: &generation.Clients{Clients: []*generation.Client{{Count: 3}}}},
+				NumSegments: 2,
+			},
+			{
+				// segments: 1:[a,b,c], 2:[d,e]
+				Month:              &generation.Data_MonthsAgo{MonthsAgo: 2},
+				Clients:            &generation.Data_All{All: &generation.Clients{Clients: []*generation.Client{{Count: 5}}}},
+				NumSegments:        3,
+				SkipSegmentIndexes: []int32{0},
+			},
+			{
+				// segments: 5:[f,g]
+				Month: &generation.Data_MonthsAgo{MonthsAgo: 1},
+				Clients: &generation.Data_Segments{
+					Segments: &generation.Segments{Segments: []*generation.Segment{{
+						SegmentIndex: &index5,
+						Clients:      &generation.Clients{Clients: []*generation.Client{{Count: 2}}},
+					}}},
+				},
+			},
+			{
+				// segments: 1:[], 2:[], 4:[n], 5:[o]
+				Month:               &generation.Data_CurrentMonth{},
+				EmptySegmentIndexes: []int32{1, 2},
+				Clients: &generation.Data_Segments{
+					Segments: &generation.Segments{Segments: []*generation.Segment{
+						{
+							SegmentIndex: &index5,
+							Clients:      &generation.Clients{Clients: []*generation.Client{{Count: 1}}},
+						},
+						{
+							SegmentIndex: &index4,
+							Clients:      &generation.Clients{Clients: []*generation.Client{{Count: 1}}},
+						},
+					}},
+				},
+			},
+		},
+	}
+
+	core, _, _ := TestCoreUnsealed(t)
+	marshaled, err := protojson.Marshal(data)
+	require.NoError(t, err)
+	req := logical.TestRequest(t, logical.CreateOperation, "internal/counters/activity/write")
+	req.Data = map[string]interface{}{"input": string(marshaled)}
+	resp, err := core.systemBackend.HandleRequest(namespace.RootContext(nil), req)
+	require.NoError(t, err)
+	paths := resp.Data["paths"].([]string)
+	require.Len(t, paths, 9)
+
+	times, err := core.activityLog.availableLogs(context.Background())
+	require.NoError(t, err)
+	require.Len(t, times, 4)
+
+	sortPaths := func(monthPaths []string) {
+		sort.Slice(monthPaths, func(i, j int) bool {
+			iVal, _ := parseSegmentNumberFromPath(monthPaths[i])
+			jVal, _ := parseSegmentNumberFromPath(monthPaths[j])
+			return iVal < jVal
+		})
+	}
+
+	month0Paths := paths[0:4]
+	month1Paths := paths[4:5]
+	month2Paths := paths[5:7]
+	month3Paths := paths[7:9]
+	sortPaths(month0Paths)
+	sortPaths(month1Paths)
+	sortPaths(month2Paths)
+	sortPaths(month3Paths)
+	entities := func(paths []string) map[int][]*activity.EntityRecord {
+		segments := make(map[int][]*activity.EntityRecord)
+		for _, path := range paths {
+			segmentNum, _ := parseSegmentNumberFromPath(path)
+			entry, err := core.activityLog.view.Get(context.Background(), path)
+			require.NoError(t, err)
+			if entry == nil {
+				segments[segmentNum] = []*activity.EntityRecord{}
+				continue
+			}
+			activities := &activity.EntityActivityLog{}
+			err = proto.Unmarshal(entry.Value, activities)
+			require.NoError(t, err)
+			segments[segmentNum] = activities.Clients
+		}
+		return segments
+	}
+	month0Entities := entities(month0Paths)
+	require.Len(t, month0Entities, 4)
+	require.Contains(t, month0Entities, 1)
+	require.Contains(t, month0Entities, 2)
+	require.Contains(t, month0Entities, 4)
+	require.Contains(t, month0Entities, 5)
+	require.Len(t, month0Entities[1], 0)
+	require.Len(t, month0Entities[2], 0)
+	require.Len(t, month0Entities[4], 1)
+	require.Len(t, month0Entities[5], 1)
+
+	month1Entities := entities(month1Paths)
+	require.Len(t, month1Entities, 1)
+	require.Contains(t, month1Entities, 5)
+	require.Len(t, month1Entities[5], 2)
+
+	month2Entities := entities(month2Paths)
+	require.Len(t, month2Entities, 2)
+	require.Contains(t, month2Entities, 1)
+	require.Contains(t, month2Entities, 2)
+	require.Len(t, month2Entities[1], 3)
+	require.Len(t, month2Entities[2], 2)
+
+	month3Entities := entities(month3Paths)
+	require.Len(t, month3Entities, 2)
+	require.Contains(t, month3Entities, 0)
+	require.Contains(t, month3Entities, 1)
+	require.Len(t, month3Entities[0], 2)
+	require.Len(t, month3Entities[1], 1)
+}