The Bolsheviks perceived the Tsarist army to be one of the foundations of the hated old regime, and decided to abolish it in favor of establishing a new military loyal to the Marxist cause. Thus the core of the Tsarist army became the core of the Russian Provisional Government army which became the core of the White Army, which in intermittent collaboration with interventionist forces from outside Russia (from Japan, Britain, France and the United States) aided the Whites and tried to contain the Red Army during the Russian Civil War. On January 28, 1918 the Bolshevik leader Vladimir Lenin decreed the establishment of the Red Army, officially merging the 20,000 Red Guards, 60,000 Latvian red riflemen with 200,000 Baltic Fleet sailors and a handful of sympathetic Petrograd garrison soldiers. Leon Trotsky served as their first commissar for war. The early Red Army was egalitarian and therefore poorly disciplined. The Bolsheviks considered military ranks and saluting to be bourgeois customs and abolished them; soldiers now elected their own leaders and voted on which orders to follow. This arrangement was abolished, however, under pressure of the Russian Civil War (1918–21), and ranks were reinstated. During the civil war, the Bolsheviks fought counterrevolutionary groups that became known as the White armies as well as armies sponsored by Russia's former allies such as the Britain and France, which saw a need to overthrow the Bolshevik government. The Red Army enjoyed a series of initial victories over their opponents, and in a surge of optimism Lenin ordered the Soviet Western Army to advance West in the vacuum created by the German forces retreating from the Ober-Ost areas. This operation swept the newly formed Ukrainian People's Republic and Belarusian People's Republic and eventually lead to the Soviet invasion of Second Polish Republic, a newly independent state of the former Russian Empire. By invading Poland and initiating the Polish-Soviet War the Bolsheviks expressed their belief that they would eventually triumph over opposing capitalist forces both at home and abroad. The overwhelming majority of professional officers in the Russian army were of nobility (dvoryanstvo); moreover, most of them had joined the White armies. Therefore, the Workers' and Peasants' Army initially faced a shortage of experienced military leaders. To remedy this, the Bolsheviks recruited 50,000 former Imperial Army officers to command the Red Army. At the same time, they attached political commissars to Red Army units to monitor