Instructions

Sleeve (make 2)
With MC and using preferred method, cast on 28[32, 32, 32, 36, 36] sts; join to work in rnds, being careful not to twist sts, place marker. 
Work in k2, p2 ribbing for 1[1, 1, 1, 1½, 1½] inches.
Knit one round.
Increase Rnd: Knit around increasing 4[0, 0, 0, 4, 4] sts evenly spaced around: 32[32, 32, 32, 40, 40] sts.

Sleeve Cuff Chart – All Sizes

 

Join CC and work Rnds 1-5 of cuff chart, working repeat 4[4, 4, 4, 5, 5] times on each rnd.
Knit 6 rnds.
Increase Rnd: K1, M1L, knit to one st before end of round, M1R, k1: 34[34, 34, 34, 42, 42] sts.
Repeat Increase Rnd every 7th rnd 1[2, 2, 3, 0, 1] time(s) more: 36[38, 38, 40, 42, 44] sts.
Knit all rnds until Sleeve measures 6½[7½, 8½, 9½, 11, 13] inches or desired length to underarm.
On final knit round, stop 3[3, 4, 4, 4, 5] sts before end of round. Place next 6[6, 8, 8, 8, 10] sts on waste yarn or holder. Place remaining Sleeve sts on separate holder and set aside.

Body

With MC and using preferred method, cast on 96[100, 112, 116, 128 144] sts; join to work in rnds, being careful not to twist sts, place marker. 
Work in k2, p2 ribbing for 1[1, 1, 1, 1½, 1½] inches.

Increase Rnd: Knit around increasing 0[2, 0, 3, 0, 0] sts evenly spaced around: 96[102, 112, 119, 128 144] sts.

Body Chart for sizes 6m, 18m, 4, 6

 

Body Chart for sizes 12m, 2T

Next Rnd: Join CC. Begin working Body chart FOR CORRECT SIZE starting at 1st[1st, 9th, 9th, 1st, 9th] st of chart, working repeat 6[6, 7, 7, 8, 9] times on each rnd.
Drop CC and using MC only, knit until piece measures 3 inches less than desired body length.

Next Rnd: Join CC. Begin working Body chart FOR CORRECT SIZE starting at 1st[1st, 9th, 9th, 1st, 9th] st of Rnd 1, working repeat 6[6, 7, 7, 8, 9] times on each rnd.
Next Rnd: With MC knit around, increasing 0[2, 0, 1, 0, 0] st(s) evenly spaced: 96[104, 112, 120, 128 144] sts.

Yoke

Join sleeves to body
It may be useful at this point to use a second 24 inch circular needle since sts will be tight once sleeves are joined.
Next Rnd: Knit 3[3, 4, 4, 4, 5] and place these on waste yarn, k19[21, 22, 24, 26, 29], bind off next 4 sts (center front), knit until there are 19[21, 22, 24, 26, 29] sts following center front bind off, place next 6[6, 8, 8, 8, 10] sts on waste yarn, pm, holding Sleeve to Body with underarm sts together, k30[32, 30, 32, 34, 34] sleeve sts, pm, k42[46, 48, 52, 56, 62], using waste yarn from first held stitches, place next 3[3, 4, 4, 4, 5] sts on waste yarn, pm, holding second Sleeve to Body with underarm sts together, k30[32, 30, 32, 34, 34] sts, pm, knit across to center front bound off sts: 140[152, 152, 164, 176, 188] sts.

At this point you will begin to work yoke back and forth.
Row 1 (WS): Purl across.
Row 2 (RS): Knit across.
Row 3 and all WS rows: Purl across.

Decrease Row (RS): * Knit to 3 sts before next marker, ssk, k1, sm, k1, k2tog; repeat from * 3 times more: 8 sts decreased – 132[144, 144, 156, 168, 180] sts.
Continue to work Decrease Row every RS row 9[10, 10, 11, 12, 13] times more, ending with a RS row: 60[64, 64, 68, 72, 76] sts.

Collar (WS): P1, (k2, p2) across to last 3 sts, k2, p1.
Work ribbing as established for 2 inches.
Bind off all sts loosely in ribbing.

Button Bands
You will now work the button band into the slit you created at the front of the sweater.
With RS facing and beginning at top edge of left front collar, pick up and knit 22[23, 23, 24, 26, 28] sts. (Note: This is approximately 2 sts for every 3 rows).
Row 1 (WS): Purl across.
Row 2: Knit aross.
Row 3: Purl across.
Rows 4 and 5: Repeat Rows 2 and 3.
Bind off all sts.

Buttonhole Flap
With RS facing and beginning at bottom edge of right front collar, pick up and knit 22[23, 23, 24, 26, 28] sts.
Row 1 (WS): Purl across.
Row 2 (Buttonhole): K3, bind off next 2 sts (one st on right needle after bind off), * k1[1, 1, 1, 2, 2] more, bind off next 2 sts (one st on right needle after bind off); repeat from * 3 times more, k0[1, 1, 2, 0, 2] sts: 5 buttonholes.
Row 3: Purl across to first group of bound off stitches, using backwards loop cast on, cast on 2 sts. Continue as established across row, casting on 2 sts over each gap.
Row 4: Knit across.
Row 5: Purl across.
Bind off all sts.

Finishing

Using tapestry needle and MC, sew down bottom edge of button bands using mattress stitch or preferred method.
Graft under arm stitches together using Kitchener stitch.
Using needle and matching thread, sew buttons onto left front button band opposite the buttonholes.
Weave in all ends. Wet block. Blocking is critical to even out the colorwork stitches.