It is all too easy in postwar accounts of the Second World War to forget that the war started over the invasion of Poland and that many Poles continued, from their defeat in September 1939 through to the end of the war in May 1945, to fight at the side of the Allies for the liberation of their country. This collective Western amnesia began with the victory parade through London to celebrate the end of the war in Europe. Polish soldiers and airmen were denied the right to march alongside the British forces they had been fighting side-by-side with a few weeks before. Although formally one of the Allied peoples, the Poles were never treated as equals.

There can be few books on the Second World War more needed than an account of just what happened to Poland and the Poles after the new state, created in 1919, was savagely obliterated by the German and Soviet armed forces in September 1939. This single-volume history by Halik Kochanski, herself the child of Polish parents who experienced the war, is a triumphant assertion of Poland’s justified place in any account of Allied victory and a fine historical monument to the millions of Poles who suffered and died for the cause of an independent Poland. That was, of course, supposed to be the cause of Britain and France too, and the putative reason for declaring war on Germany, but Poland was the occasion, rather than the cause, of war for the West. Fighting Hitler to preserve Anglo-French interests was paramount. In Anglo-French staff planning it was always assumed that Poland could be reconstituted once the war was over – if it was still there.

Kochanski is clear that there are many accounts to be settled with the way the Poles were treated by every combatant power – indifferently by the West, diabolically by Hitler and Stalin – but there is nothing strident or polemical about this history. She tells it as it was, and a shocking story it is. Poland’s integrity was guaranteed accidentally in March 1939 because Chamberlain was in a hurry to stress the limits of British patience after the occupation of Prague. Little effort was made to coordinate war planning or preparation with the Polish military, the modest £8 million of aid the Poles asked for could not be put to use, and when Germany invaded on 1 September (followed by the USSR just over two weeks later), scant effort was made in the West to attack Germany to ease the pressure on Poland. The Poles were the first country to fight Hitler rather than kowtow, but they fought on their own.

Poland was divided between the two dictatorships, German and Soviet, and treated abominably by both. The story of how Polish national life was snuffed out is better known now than it was, thanks to the opening of Soviet archives. The German colonisers closed down schools and universities, took over Polish businesses wholesale, dispossessed hundreds of thousands, and murdered in cold blood the members of the national, political and intellectual elite who fell into their hands. Polish POWs were so much slave labour. The Soviet Union treated the Polish population no differently. Hundreds of thousands were deported to camps and labour colonies in Siberia or Kazakhstan where they died of cold and hunger, or lived lives of unimaginable squalor. Among the most vivid and original passages in this powerfully written narrative are the rich descriptions by those who suffered Soviet exile. How any survived at all seems little short of miraculous.

It is still historically puzzling why the Germans and the Soviets hated the Poles so much and could treat them with such calculated brutality and primitiveness, a question that Kochanski might have reflected on herself. The Soviet case is easier to understand, for Stalin was one of the Bolshevik representatives at the front in 1920 when the Poles inflicted the decisive defeat on the Red Army and prevented the Bolshevisation of Poland. It is clear Stalin never forgot or forgave that reverse. The Poles had also been reluctant to show any sympathy to the Soviet Union in the 1930s, a fact that persuaded some German leaders that Poland might easily become another German satellite in the European anti-communist bloc. Poland would not play ball here either, which perhaps explains Hitler’s fury. But there were links between Poles and Germans, and decent relations for much of the 1930s. The sudden change to violent colonisers surprised the Poles and it is not evident now why it happened.

The second half of The Eagle Unbowed explores the way Poles fought back against the German enemy. Many soldiers, airmen and sailors escaped in 1939, but were not made particularly welcome in the West. In France they were given filthy accommodation and poor resources for training, but when they were allowed to fight, proved themselves brave to a fault (Kochanski cites Pétain wishing he had had ten Polish divisions instead of only one). Some were captured in 1940, but others made their way by a number of ingenious routes to Britain, where they were finally allowed to form a proper Polish army and to fly in Fighter Command. The Polish squadrons became the highest scorers in the Battle of Britain (George VI remarked how good it might have been ‘if all our Allies had been Poles’). But in general the Poles had a raw deal, kicking their heels in Britain waiting to invade or, in the case of thousands more soldiers released by Stalin from captivity and sent to the Middle East, fighting Italians in north Africa instead of getting at their real enemies.

Poles fought bravely, over and above the regular call of duty in the British armed forces, and suffered heavy losses for little credit. They stormed the hill at Monte Cassino when all the rest had failed, but it was the Union Jack, not the red and white Polish flag, that was unfurled on the top, and a ‘British’ victory that was hailed in the British press. Kochanski makes it clear that even in the West, among apparent friends, the Poles were regarded as awkward comrades. General Sikorski, head of the government in exile, was a difficult presence during the delicate negotiations with Stalin, while Polish units were widely regarded as poorly disciplined and ungrateful. Little help was given when the Polish Home Army revolted in Warsaw in August 1944, as forlorn a struggle as the one in September 1939. When Stalin turned the screw late in 1944 to get the West to accept Soviet plans for pushing Poland geographically westwards, and taking all that had been gained in 1939–40 for the Soviet Union, the London Poles were more or less abandoned and tacit acceptance was given to Stalin’s new ‘people’s committee’, which was dominated by communists. Fighting so desperately against the German enemy for Britain and America’s benefit brought the Poles nothing.

It is hard not to see Poland’s fate in the Second World War in tragic terms. Kochanski cites a German SS man in 1943 concluding that the oppression borne by the Poles ‘has never been borne by any other nation’, and he should have known. But Halik Kochanski also shows how Polish national sentiment, social solidarity and family ties could survive even the most terrible of experiences. Though both oppressors would have happily extinguished the Polish nation, and the democratic West was willing to sacrifice it when it suited, Poland was still there when victory was declared, the only country to fight for every single day of the European war against Germany. The story of that fight deserves to be better known – now, at last, it will be.