The pivotal point of the attack would be the crossing of the Gari River and bursting through the Gustav Line. This formidable defensive line stretched from the west coast of Italy and was anchored on Monte Cassino.

In the centre of the attacking force was the 8th Indian Division with the 1st Canadian Armoured Brigade in support. The question was how to get bridges across the Gari River. It was the ingenuity of a young Canadian officer, Captain Kingsmill that solved the dilemma.

During the Italian Campaign of the Second World War, as the Allies moved northwest from where they had landed at Italy’s southwestern tip in early September 1943, they confronted German forces who regularly retreated back to predetermined and heavily fortified defensive lines. Consequentially, Allied armies had to break each of these lines in turn, and often at great cost.

The Gari River marked the eastern edge of the Gustav Line. The German Army used the river and the sloping ridge behind it as part of a defensive network that included artillery, mortars, machine gun posts, trenches and bunkers. Both sides of the river had also been heavily mined.

The Gari, a swiftly-flowing river that ranges between 40 to 60 feet in width and about six to eight feet in depth, served as a natural tank trap. The river banks were also open and flat, offering the infantry no cover. But if they were going to break the Gustav Line, the Allies first had to get across the Gari, something they had tried—and failed—on previous occasions.

The attack on the Gustav Line that began in May 1944 was part of a much larger offensive involving two armies, the British 8th and US 5th armies, along a front that stretched across Italy from the Tyrrhenian Sea in the west to the Adriatic Sea in the east.

Allied planners designed the fourth attack to begin during the night of May 11/12 with infantry regiments from the British 4th Infantry Division and 8th Indian Division crossing the river under the cover of darkness to establish bridgeheads. The infantry attack went in under cover of a massive artillery bombardment.

Two armoured regiments, the Calgary Tanks and the Ontario Regiment, meanwhile, were tasked with crossing pre-fabricated bridges, known as Bailey bridges, at dawn to reinforce the infantry and secure the bridgeheads. The armoured and infantry regiments were to then expand the bridgeheads, breaking the line.

The Calgary Regiment had been tasked with supporting the Argyle and Southern Highlanders and the 3/8 Punjab Regiment of the 19th Infantry Brigade. These infantry regiments were to cross the river south of the town of San Angelo and then swing south towards Panaccioni and clear the junction of the Garigilano and Liri Rivers.

The Calgary Regiment's 'A' Squadron had been assigned to support the Argyle and Southern Highlanders, while 'C' Squadron would join the 3/8 Punjabis. 'B' Squadron, meanwhile, would be held in reserve. The tanks of the Ontario Regiment were to cross the river and turn north to support the three battalions of the 17th Infantry Brigade. The success of this attack relied on getting the bridges erected and getting the tanks over those bridges.

Initially, in pre-planning, the attack had been built around two bridges—codenamed Cardiff and Oxford—capable of supporting the weight of the 30-ton Sherman tanks used by the Calgary and Ontario regiments.

Cardiff would go in north of the village of San Angelo and Oxford would be erected over the river south of the village; however, this did not sit well with Lt.Col. C.H. Neroutsos, the Calgary Tank's commanding officer, as both bridges were north of where the Argyle and Southern Highlanders and the 3/8 Punjabis would cross the river to establish their bridgeheads.

"I was not at all happy with this and told General Russell that I didn't think I could give him the support he expected over a crossing of that nature, so we had many discussions about it," Neroutsos wrote.

But planners faced two problems: The engineers were short of bridging materials and the best location for Neroutsos's bridge was a spot where the German defenders held the line only 300 metres from the river. The proximity of the German lines would have made it practically impossible for sappers to erect a bridge.

"During one of these discussions," wrote Neroutsos, "Lt.Col Schoolhouse, who was GSO 1 (general staff officer) to General Russell and a friend of mine said, 'Well, why can't we build a Bailey Bridge and push it across the damn river—it's only a couple of a hundred yards wide!' And we thought that was very funny."

But Schoolhouse's off-the-cuff comment got Neroutsos thinking. He approached Tony Kingsmill, a 24-year-old chemical engineer with training in mechanical engineering to see if there would be a way, as Schoolhouse suggested half-jokingly, to push a completed bridge across the Gari River rather than erect it in place. Kingsmill commanded the 61st Light Aid Detachment, Royal Canadian Electrical and Mechanical Engineers, which was attached to the Calgary Tanks.

I put this hair-brained idea to Kingsmill. He took it back and mulled it over and came back with the idea of one tank holding the front end of the Bailey Bridge while the other was pushing it," wrote Neroutsos.

Initially, Kingsmill wrote that he did not think much of the idea of using tanks to launch a large bridge, but he began experimenting with it weeks before the attack in the Voltunro Valley to see if it could work.

The idea was not without precedent, however, as the Allies were already using hybrid tanks, known as Funnies, that had been modified for specific tasks such as mine clearing or bridging.

But in the case of bridging tanks, they could only cover a 30 foot gap. The river at the location proposed for the Calgary Regiment measured 57 feet wide. And no one had ever attempted using two tanks to carry and launch a bridge.

With the help of a platoon of Royal Sikh Engineers and four tanks from the Calgary Regiment, along with four tank drivers and a wireless operator, Kingsmill built a prototype and successfully tested it first in a field and then on May 5 at a nearby river. He had just under a week to get his bridge ready for the assault on the Gustav Line.

On May 11, the night of the attack, engineers moved to prepare a site for bridge construction roughly a half-kilometre from the river, but the numerous mines; the soft, muddy ground; and the heavy fog hampered their progress. The Calgary Regiment had hoped to have the bridge in place over the Gari River by 4 a.m., but the bulldozers that would be used to clear and level the construction site didn't arrive until 3:50 a.m.

The carrier tank, meanwhile, got lost in the fog, smoke and darkness and didn't reach the site until 5 a.m. Finally, the trucks hauling the bridging supplies were also late; they arrived at 5:30 a.m. and one of the trucks overturned on the way there.

Once the vehicles and supplies were all accounted for, Kingsmill and his crew of bridge engineers from the 8th Indian Division got to work. They erected the 100-ft.-long, 30-ton bridge on a heavy steel 20-ft.-long frame constructed of I-beams and rollers mounted to the turret-less carrier tank. The pusher tank was attached to the end of the bridge by a collar that could be blown apart with C4 explosive ignited by an electrical trigger from inside the tank.

Once the bridge was ready, the two tanks set off for the river on May 12 at about 6 a.m. with Kingsmill using a radio to guide both tanks through the fog. Ian Seymour, the wireless operator in the carrier tank wrote that "Captain Kingsmill took his place on the ground to the left of this huge ungainly contraption and ordered both tanks to advance. With many a creak and a groan, the whole moved slowly forward."

As the tanks crawled towards the river carrying their ungainly load along a route cleared of mines and marked with white tape, the carrier tank sank into the mud. Engineers struggled for three hours to free the tank and get the entire assembly moving again. The tanks and the bridge finally reached the riverbank shortly before 9:30 a.m. just as the fog began to lift. And even though engineers laid down a smoke screen, the German defenders caught sight of the tanks and the bridge and began firing with small arms and mortars.

The gunfire and explosions forced Kingsmill to seek cover in the carrier tank with radio operator Trooper Ian Seymour and driver Trooper George MacLean. MacLean stopped the carrier tank at the edge of the swollen river and the pusher tank slowly began to move forward, driving the bridge across the river. As the bridge began to move forward on the rollers, Kingsmill ordered the carrier tank forward to keep it from getting bogged down in the soft ground along the river.

The Sherman plunged into the river and sank. MacLean clambered from the flooded tank by way of the driver's hatch. He swam across the river, as did Kingsmill. Seymour reached the bank of the river by scrambling hand-over-hand underneath the bridge.

The crew of the pusher tank blew the C4 explosive packed around the bracket that connected the tank to the bridge. The end of the bridge fell to the ground with an enormous crash and the pusher tank backed off. Kingsmill, MacLean and Seymour took shelter in the pusher tank. Kingsmill radioed Lt.-Col. Neroutsos at about 10 a.m. to tell him that the bridge was in place and ready for use.

Initially, Neroutsos had intended that 'A' Squadron would cross Plymouth bridge at dawn—about 6 a.m.—followed by 'C' Squadron with 'B' Squadron in reserve. But the delay in getting Plymouth bridge launched meant Neroutsos had to adjust his plans.

The 3/8 Punjabis and the Argyle and Southern Highlanders had been fighting without the support of tanks since midnight. They were on the brink of being wiped out. Capt. Jim Quinn, who led 'A' Squadron, wrote: "The Punjabis were heard from at about 0400 hours and were meeting heavy resistance and suffering severe casualties.

Because of the delays with the tank bridge it was decided to switch 'C' Squadron, which was to have crossed our bridge first, up to Oxford bridge near Sant Angelo in the 17 Infantry Brigade sector."

At about 8:30 a.m., 'C' Squadron of the Calgary Regiment moved to Oxford Bridge in fog and smoke so dense that the crews couldn't see the bridge or the west bank of the river. The two leading 'C' Squadron tanks, commanded by Lt. R.A. Cawsey and Cpl. Bill McWithey approached the bridge and prepared to cross.

Tanks with the Ontario Regiment had crossed Oxford bridge earlier that morning. As planned, they had moved north to assist the infantry attacking San Angelo; however, 15 of those the Ontario tanks, about half of the Ontario tanks that had crossed Oxford, had become stuck in the mud and soft ground and required extraction.

"According to our pre-arranged plan, my Corporal, Bill McWithey, was to lead to the bridge, and after the crossing I would take over the lead. My squadron leader, Don Taylor, came up to me and waved us ahead. We crossed the hill about 200 yards south of the Gari and followed a route marked by the Engineers and Provost with white tape," wrote Cawsey. "The Gari River was at a very high level and the last 100 yards before the river it was very muddy.

As soon as Bill McWithey hit the mud he got stuck. There were no other engineers in sight, and we were under heavy artillery and mortar fire and some machine gun fire. I decided to direct my tank around to the right of Bill's, keeping my fingers crossed and praying that I wouldn't hit a mine, because if we didn't get across the bridge, it would be the end of our Indian infantry."

Cawsey's co-driver, Trooper Price, got out of the tank and walked ahead of it searching for mines. The tank crept around McWithey's tank and, using the tow cable, pulled the stuck tank free of the mud. Cawsey later learned that his tank had straddled at least three mines as it maneuvered past the stuck tank.

"The ground was so soft, that Bill and I were the only ones to get across the bridge for several hours—so we had the German Army all to ourselves," wrote Cawsey. "As soon as we crossed the bridge, we saw bodies of the Americans who had tried twice to cross the river during the first battle for Cassino."

Cawsey reached a company of the 3/8 Punjabis as directed and discovered that of the eighty men who had been with that company at the start of the attack, only ten were left.

"I reported the situation to my Squadron Leader, Major Don Taylor, and he told me that he was stuck, that no more tanks or infantry could get across the bridges so we were on our own... We decided to push on to our original objective, which was Panaccioni."

With the rest of 'C' Squadron trapped on the south side of the Gari River, Cawsey and McWithey continued to help the 3/8 Punjabis. The two tanks knocked out machine gun posts and several 75 mm self-propelled guns, and without infantry to support them, they continued to Panaccioni. After a second report to Major Taylor, Cawsey learned Plymouth Bridge had been damaged and to expect no support for a few hours.

"(Taylor) further explained that since we were the only troops in the area, we could have all of the artillery support we wanted. We wanted to preserve our own ammunition so for a couple of hours I was directing the fire of about 300 artillery pieces, or could have had the artillery of the whole 8th Army if I had wanted it."

Despite having the ability to direct artillery strikes, Cawsey and McWithey used their own high-explosive shells to attack a building they suspected was being used as a headquarters.

The two Shermans commanded by Cawsey and McWithey were the sole Calgary tanks on the north side of the river for at least an hour and a half until tanks from 'A' Squadron began crossing Plymouth Bridge once it had been launched at 10 a.m. It was slow going for 'A' Squadron as it attempted to get its tanks across Plymouth Bridge.

Because the carrier tank didn't sink as deeply into the river as expected, the bridge sat like a teeter-tooter and only one tank could cross at a time. Four 'A' Squadron tanks managed to cross Plymouth Bridge before it was damaged by German artillery shells.

Kingsmill, MacLean and Seymour, using the spare carrier tank, raced back to the construction site for bridge parts. They returned with a small group of Indian sappers and supplies to repair the bridge. But as the men unloaded the bridging parts, a German machine gun opened fire, hitting one of the sappers in the stomach.

Bullets spattered against the tank and the steel bridge parts, breaking into tiny pieces of shrapnel. Shrapnel hit Seymour in the face and across his back. Medics used a Jeep ambulance to evacuate Kingsmill and the other casualties. One of the tank crew members and five sappers were wounded and three sappers were killed in the attack.

With the bridge closed for repairs, Capt. Jim Quinn, who was now on the west side of the river, wrote that the rest of 'A' Squadron was "now lined up nose to tail in the cleared lanes back of the bridge... concern that the enemy in the Liri Appendix would have some good shooting if there was a break in the smoke screen.

The Squadron was ordered to reverse out along the cleared lanes and to move north and cross, as 'C' Squadron had done, over the Oxford bridge. Once over the bridge they would swing left along the road and join up with the rest of the squadron and our infantry.

"During the remainder of the day 'A' Squadron, with considerable difficulty and enemy harassing fire, were able to extricate themselves from the assault bridge and cross over Oxford to the far bank. A considerable number of tanks became bogged down and four were lost to mines in the process," wrote Quinn.

With the bridge repaired and Kingsmill and the other injured sappers removed from the battlefield, 'B' Squadron, led by Major Fred Ritchie, began crossing the Gari.

The Calgary Regiment now had eight tanks on the west side of the river, four from both 'A' and 'C' squadrons. Major Don Taylor, 'C' Squadron commanding officer, managed to get across along with one other tank from his squadron, but the rest of 'C' Squadron remained stuck on the east side of the river.

Jim Quinn, commanding the fourth 'A' Squadron tank to cross Plymouth Bridge, and the other three tanks from his squadron that crossed before him, were unable to find the Argyle and Southern Highlanders. The four 'A' Squadron tanks, heavily camouflaged with branches, stopped outside Panaccioni within site of a building that was being used as a headquarters and dressing station.

The tank crews watched as enemy vehicles and infantry moved towards the villages of Pignataro and Sant Angelo, and just as Cawsey and McWithey did earlier in the morning, the 'A' Squadron tankers directed artillery fire down upon the vehicles and infantry. The Calgary Tanks refrained from firing until a section of German soldiers walked past and recognized, on second glance, that the tanks were not their own.

"They now knew where we were and we opened fire. I allocated areas to the other vehicles and we commenced to shoot up everything we could see or that moved," wrote Quinn, adding that enemy artillery and mortar fire quickly began rain down on them.

The four tanks destroyed the building but the crew inside these machines began to realize how exposed they were faced with artillery, mortar and small arms fire with infantry to protect them from enemy soldiers.

"…we were very exposed and facing increasing pressure. The enemy had to worry about our infantry but it must have been obvious by now that they (the British and Indian infantry) were not there," wrote Quinn.

"The same thought about our general exposure and vulnerability must have been going through the Infantry Brigade and Regimental Headquarters for at 1700 hours we were ordered, as was 'C' Squadron, to withdraw back to the line of the Sant Angelo/Sant Apollinare Road."

The eight tanks returned to the river to refuel and re-arm and wait for morning. Unlike 'A' Squadron, the tanks of 'C' Squadron did link up with the infantry that evening. Al Cawsey, commander of the first Calgary tank across the river, wrote: "A few of the infantry threw up a circle around us, but we had to stay on guard on all night, because there were still plenty of Germans around.

Each member of the crew stood guard duty for two hours. After the day we had spent it was hard to stay awake."

Just before dawn on 12 May, 1944 following a long, tense night, Cawsey wrote that Major Gudari Singh of the 3/8 Punjabis asked if the tanks could move up the hill to help fend off a suspected counter attack.

Cawsey's tank moved up the hill into position, and as he searched the area through his binoculars for enemy activity he "felt as if someone had tried to stick a red-hot needle through me." Cawsey fell into the tank. He had been hit by shrapnel from a mortar bomb.

'C' Squadron commanding officer Major Don Taylor told Cawsey to give command of his tank to his gunner and have the tank bring him to Plymouth Bridge where he was evacuated to the Regimental Aid Post and then to a hospital. Cawsey did not return to the Calgary Regiment until the end of June 1944.

Meanwhile, the 'C' Squadron tanks moved up the hill to guard against a possible counterattack where Jim Quinn and the four other 'A' Squadron tanks met up with the rest of 'A' Squadron and with the Argyle and Southern Highlanders early in the morning.

'B' Squadron and the headquarters squadron of the Calgary Regiment finally crossed the Gari River the following day, on May 13, and with 'A' Squadron they took Panaccioni. 'C' Squadron, however, did not cross the river until much later as, with the exception of the four tanks on the west side of the river, the remaining 12 tanks of 'C' Squadron were still "mucked down" at Oxford Bridge or had been damaged by mines.

Without Plymouth Bridge, it is possible the attack on the Gustav Line would have failed, as the previous attacks had. Construction on Cardiff Bridge was suspended at dawn due to intense machine gun and mortar fire. London Bridge (to be installed during the night of May 12-13) at San Angelo, just north of Oxford bridge, had to be delayed as the Germans still held San Angelo.

Plymouth Bridge, however, allowed the Calgary Tanks to get enough tanks across to fulfill its objectives and clear the Liri Appendix, which helped the Allies break the Gustav Line. By the end of the attack on the Gustav Line, the Calgary Regiment saw 56 of is personnel wounded and 60 tanks damaged.

Lt.Col. Neroutsos wrote that Lt.Gen. Dudley Russell, commanding officer of the 8th Indian Div., told him well after the war that Plymouth Bridge was one of the pivotal pieces. "General Russell was convinced that us getting through almost a whole regiment of tanks on the German left flank was one of the basic things that enabled the 8th Army to cross the Gari River. As you know the break-through for Cassino came later and was a great success,"

Neroutsos wrote. "I also think I should add that, due to the (Plymouth) Bridge and our rapid advance to the sector that the 8th Army allotted to us for crossing the Melfa River, we got there at least two days ahead of time and captured a bridge over the Melfa intact. Then the British Sixth Armoured Division went through and the Canadians and other people further south of us fought for two or three days later for a crossing of the Melfa River."

Following the breaking of the Gustav Line, a number of members of the Calgary Regiment were recognized for their effort and actions: Majors Fred Ritchie and Don Taylor each received the Military Cross; Trooper George MacLean received the Military Medal while Trooper Ian Seymour was Mentioned in Despatches.

For his part, Tony Kingsmill received the Military Cross. He recovered from his wounds and rejoined the Calgary Tanks a month after the attack at the Gari River. After the war, he pursued his doctorate degree in engineering. He bought a cabin in Whistler, B.C. in 1968, and later becoming a permanent resident and working as a real estate agent until he retired and moved to Vancouver.

The bridge he designed became forever known as the "Kingsmill Bridge".

In 2007, at the age of 87, Tony Kingsmill returned with members of the Regimental Association to the Gari River for the first time since the war to commemorate alongside the 63rd anniversary of the river crossing. A bronze plaque was unveiled in honour of the Kingsmill Bridge.

A permanent marble monument incorporating the first bronze plaque was unveiled in 2012 very near the site of the crossing. Dedicated to Lt. Al Cawsey, the monument pays tribute to the Kingsmill Bridge and the accomplishments of the 1st Canadian Armoured Brigade in the breakthrough of the Gustav Line.